Scientific Publications

Author(s): Samuel Shephard, Simon P.R Greenstreet, GerJan. Piet, Anna Rindorf, Mark Dickey-Collas.

Title: Surveillance indicators and their use in implementation of the Marine Strategy Framework Directive 

The European Union Marine Strategy Framework Directive (MSFD) uses indicators to track ecosystem state in relation to Good Environmental Status (GES). These indicators were initially expected to be “operational”, i.e. to have well-understood relationships between state and specified anthropogenic pressure(s), and to have defined targets. Recent discussion on MSFD implementation has highlighted an additional class of “surveillance” indicators. Surveillance indicators monitor key aspects of the ecosystem for which there is: first, insufficient evidence to define targets and support formal state assessment; and/or second, where links to anthropogenic pressures are either weak or not sufficiently well understood to underpin specific management advice. Surveillance indicators are not only expected to directly track state in relation to GES, but also to provide complementary information (including warning signals) that presents a broader and more holistic picture of state, and inform and support science, policy, and management. In this study, we (i) present a framework for including surveillance indicators into the Activity–Pressure–State–Response process, (ii) consider a range of possible indicators that could perform this surveillance role, and (iii) suggest criteria for assessing the performance of candidate surveillance indicators, which might guide selection of the most effective indicators to perform this function.Internation

Permanent Identifier: http://icesjms.oxfordjournals.org/content/early/2015/07/18/icesjms.fsv131.abstract?keytype=ref&ijkey=VG8RIHk8zgzXbO3

 

Author(s): Verena M.Trenkel, Niels T.Hintzen, Keith D.Farnsworth, Christian Olesen, David Reid, Anna Rindorf, Samuel Shephard, Mark Dickey-Collas.

Title: Identifying marine pelagic ecosystem management objectives and indicators

International policy frameworks such as the Common Fisheries Policy and the European Marine Strategy Framework Directive define high-level strategic goals for marine ecosystems. Strategic goals are addressed via general and operational management objectives.To add credibility and legitimacy to the development of objectives,for this study stakeholders explored intermediate level ecological, economic and social management objectives for Northeast Atlantic pelagic ecosystems.Stakeholder workshops were undertaken with participants being free to identify objectives based on their own insights and needs.Overall 26 objectives were proposed,with 58% agreement in proposed objective between two workshops.Based on published evidence for pressure-statelinks,examples of operational objectives and suitable indicators for each of the 26 objectives were then selected.It is argued that given the strong species-specific links of pelagic species with the environment and the large geographic scale of their lifecycles,which contrast to demersal systems,pelagic indicators are needed at the levelof species (orstocks) independent of legislative region.Pelagic community indicators may be set at regional scale in some cases.In the evidence-based approach used in this study,the selection of species or region specific operational objectives and indicators was based on demonstrated pressure-statelinks. Hence observed changes in indicators can reliably inform on appropriate management measures.

Permanent Identifier: http://www.sciencedirect.com/science/article/pii/S0308597X15000044

 

Author(s): Hegland, T.J & Hopkins, C.C.E. 

Title: Towards a new fisheries effort management system for the Faroe Islands? - Controversies around the meaning of fishing sustainability

The Faroe Islands are currently struggling to find their feet in a new context of globalisation and changing international requirements on fishery management best practices, as exemplified by United Nations protocols and agreements. We introduce the Faroese fisheries effort management system for cod, haddock and saithe, which represents an innovative attempt to tackle the challenges of mixed fisheries by means of a combination of total allowable effort implemented through days-at-sea and extensive use of closed or limited access areas. Subsequently, we present and discuss controversies concerning the system’s ability (or lack thereof) to achieve a level of fishing effort that produces long-term sustainability. Over the years the system has proved able to evolve and overcome challenges, and the Faroe Islands are currently considering adding a proper fisheries management plan to the system to achieve fishing at maximum sustainable yield. However, finding support for this plan presents a challenge due particularly to an enduring gap between the perspectives of scientists and actors in the catching sector. Finally, we outline some actions that could be taken to reduce the gap and hence facilitate reform of the system: 1) integration of the consultative/advisory process; 2) obtaining tailor-made advice for the Faroese effort management system from the relevant scientific body; 3) establishment of a transparent mechanism for monitoring and regulating fishing effort; 4) clarifying the efficacy of the prevalent system of closed areas.

Permanent Identifier: http://link.springer.com/article/10.1186/s40152-014-0012-7/fulltext.html  

 

Author(s): Thorsten Blenckner, Marcos Llope, Christian Möllmann, Rudi Voss, Martin F. Quaas, Michele Casini, Martin Lindegren, Carl Folke, Nils Chr. Stenseth

Title: Climate and fishing steer ecosystem regeneration to uncertain economic futures 

Overfishing of large predatory fish populations has resulted in lasting restructurings of entire marine food webs worldwide, with serious socio-economic consequences. Fortunately, some degraded ecosystems show signs of recovery. A key challenge for ecosystem management is to anticipate the degree to which recovery is possible. By applying a statistical food-web model, using the Baltic Sea as a case study, we show that under current temperature and salinity conditions, complete recovery of this heavily altered ecosystem will be impossible. Instead, the ecosystem regenerates towards a new ecological baseline. This new baseline is characterized by lower and more variable biomass of cod, the commercially most important fish stock in the Baltic Sea, even under very low exploitation pressure. Furthermore, a socio-economic assessment shows that this signal is amplified at the level of societal costs, owing to increased uncertainty in biomass and reduced consumer surplus. Specifically, the combined economic losses amount to approximately 120 million € per year, which equals half of today's maximum economic yield for the Baltic cod fishery. Our analyses suggest that shifts in ecological and economic baselines can lead to higher economic uncertainty and costs for exploited ecosystems, in particular, under climate change.

Permanent Identifier: http://rspb.royalsocietypublishing.org/content/282/1803/20142809

 

Author(s): Da Rocha, José María and Mato Amboage, Rosa

Title: On the Benefits of Including Age-structure in Harvest Control Rules 

This paper explores the benefits of including age-structure in the control rule (HCR) when decision makers regard their (age-structured) models as approximations. We find that introducing age structure into the HCR reduces both the volatility of the spawning biomass and the yield. Although at a fairly imprecise level the benefits are lower, there are still major advantages for actual assessment precision of the case study. Moreover, we find that when age-structure is included in the HCR the relative ranking of different policies in terms of variance in biomass and yield does not differ. These results are shown both theoretically and numerically by applying the model to the Southern Hake fishery.

Permanent Identifier: https://addi.ehu.es/handle/10810/13257

 

Author(s): Gorka Merinoa, Antoni Quetglasc, Francesc Maynoud, Antoni Garaue, Haritz Arrizabalagaa, Hilario Muruaa, Josu Santiagof, Manuel Barangeb, Raúl Prellezof, Dorleta Garcíaf, Jordi Lleonartd, Georges Tserpesg, Christos Maraveliash, Natacha Carvalhoi, Melanie Austenb, Jose A. Fernandesb, Pere Oliverc, Antoni Maria Grauj

Title: Improving the performance of a Mediterranean demersal fishery toward economic objectives beyond MSY

Mediterranean demersal fisheries are highly multispecific and many of their target stocks are overexploited. In addition, rocketing fuel costs and low market prices of traditionally high-value species are challenging the viability of fisheries. Here, based on the numeric results of a simulation model, we conclude that this situation can be remedied by reducing both fishing mortality and fishing costs. According to our model results, fishing effort reductions of 48–71% would improve the health of fish stocks while increasing the economic profits of Mallorca islands bottom trawl fishery to as much as 1.9 M€ (146% higher than current profits). If all fish stocks were exploited at their MSY (or below) level, the reduction in fishing effort would have to be of 71% from current values. If equilibrium profits from the fishery were to be maximized (MEY), fishing effort would need to be reduced by 48%. These results must be taken with caution due the many sources of uncertainty of our analysis. The modeling tools used to estimate these values are conditional to the adequate treatment of two sources of uncertainty that are particularly problematic in Mediterranean fisheries: insufficiently known recruitment variability and lack of periodic evaluations of the state of many species. Our results show that fishing effort reductions would produce economic yield gains after a period of transition. Further studies on the benefits of changing the size-selection pattern of fisheries, on better estimation of stock–recruitment relationships and on better quantifications of the contribution of secondary species to these fisheries, are expected to improve the scientific recommendations for Mediterranean demersal fisheries toward sustainability principles.

Permanent Identifier: http://www.sciencedirect.com/science/article/pii/S0165783614001982

 

Author(s): Tak Fung, Keith D. Farnsworth, David G. Reid & Axel G. Rossberg

Title: Impact of biodiversity loss on production in complex marine food webs mitigated by prey-release 

Public concern over biodiversity loss is often rationalized as a threat to ecosystem functioning, but biodiversity-ecosystem functioning (BEF) relations are hard to empirically quantify at large scales. We use a realistic marine food-web model, resolving species over five trophic levels, to study how total fish production changes with species richness. This complex model predicts that BEF relations, on average, follow simple Michaelis–Menten curves when species are randomly deleted. These are shaped mainly by release of fish from predation, rather than the release from competition expected from simpler communities. Ordering species deletions by decreasing body mass or trophic level, representing ‘fishing down the food web’, accentuates prey-release effects and results in unimodal relationships. In contrast, simultaneous unselective harvesting diminishes these effects and produces an almost linear BEF relation, with maximum multispecies fisheries yield at ?40% of initial species richness. These findings have important implications for the valuation of marine biodiversity

Permanent Identifier: http://www.nature.com/ncomms/2015/150323/ncomms7657/full/ncomms7657.html?WT.ec_id=NCOMMS-20150325 

 

Author(s): José-María Da Rocha, María-José Gutiérrez, Sebastian Villasante

Title: Economic effects of global warming under stock growth uncertainty: the European sardine fishery

Global warming of the oceans is expected to alter the environmental conditions that determine the growth of a fishery resource. Most climate change studies are based on models and scenarios that focus on economic growth, or they concentrate on simulating the potential losses or cost to fisheries due to climate change. However, analysis that addresses model optimisation problems to better understand the complex dynamics of climate change and marine ecosystems is still lacking. In this paper, a simple algorithm to compute transitional dynamics in order to quantify the effect of climate change on the European sardine fishery is presented. The model results indicate that global warming will not necessarily lead to a monotonic decrease in the expected biomass levels. Our results show that if the resource is exploited optimally, then in the short run, increases in the surface temperature of the fishery ground are compatible with higher expected biomass and economic profit.

Permanent Identifier: http://link.springer.com/article/10.1007/s10113-013-0466-y

 

Author(s): Ole Ritzau Eigaard, Paul Marchal, Henrik Gislason, and Adriaan D. Rijnsdor

Title: Technological Development and Fisheries Management

Many marine fish stocks are overexploited and considerable overcapacity exists in fishing fleets worldwide. One of the reasons for the imbalance between resource availability and fishing capacity is technological development, which continuously increases the efficiency of the vessels—a mechanism referred to as “technological creep.” We review how the introduction of new and more efficient electronic equipment, gear design, engines, deck equipment, and catch-handling procedures influences the capture efficiency (catchability) of commercial fishing vessels. On average, we estimate that catchability increases by 3.2% per year due to technological developments, an increase often ignored in fisheries management. The documentation and quantification of technological creep improves the basis for successfully integrating the effects of technological development (and catchability changes) in fisheries management regulations and policies. Ways of counteracting the undesired effects of technological creep are discussed as are the potential management benefits from improved fishing technology. Specific suggestions are given on the selection, application, and tuning of fisheries management tools that can be used to improve the balance between harvesting capacity and resource availability.

Permanent Identifier: http://www.wageningenur.nl/en/Publication-details.htm?publicationId=publication-way-343533363239

 

Author(s): Samuel Shephard, David G. Reid, Hans D. Gerritsen, and Keith D. Farnsworth

Title: Estimating biomass, fishing mortality, and “total allowable discards” for surveyed non-target fish 

Demersal fisheries targeting a few high-value species often catch and discard other “non-target” species. It is difficult to quantify the impact of this incidental mortality when population biomass of a non-target species is unknown. We calculate biomass for 14 demersal fish species in ICES Area VIIg (Celtic Sea) by applying species- and length-based catchability corrections to catch records from the Irish Groundfish Survey (IGFS). We then combine these biomass estimates with records of commercial discards (and landings for marketable non-target species) to calculate annual harvesting rates (HR) for each study species. Uncertainty is incorporated into estimates of both biomass and HR. Our survey-basedHRestimates for cod and whiting compared well with HR-converted fishing mortality (F) estimates from analytical assessments for these two stocks. Of the non-target species tested, red gurnard (Chelidonichthys cuculus) recorded some annual HRs greater than those for cod or whiting; challenging “Pope’s postulate” that F on non-target stocks in an assemblage will not exceed that on target stocks. We relate HR for each species to two corresponding maximum sustainable yield (MSY) reference levels; six non-target species (including three ray species) show annual HRs ? HRMSY. This result suggests that it may not be possible to conserve vulnerable non target species when F is coupled to that of target species. Based on biomass, HR, and HRMSY, we estimate “total allowable catch” for each non-target species.

Permanent Identifier: http://icesjms.oxfordjournals.org/content/early/2014/08/27/icesjms.fsu146.full

 

Author(s): M. Begoña Santos, Camilo Saavedra, Graham J. Pierce

Title: Quantifying the predation on sardine and hake by cetaceans in the Atlantic waters of the Iberian peninsula 

Construction of ecosystem models requires detailed information on trophic interactions which may not be readily available, especially for top predators such as cetaceans. Such information can also be useful to estimate natural mortality (M) for fish stock assessments and to evaluate the potential for competition between cetaceans and fisheries. In the present paper we provide estimates and confidence limits, taking into account sampling error, for consumption of fish by the four most common cetaceans along the Atlantic coast of the Iberian Peninsula, while highlighting the uncertainties and biases inherent in the information presently available on energy requirements, diet and population size. We estimated that common dolphins (Delphinus delphis) consume around 6800 (95% CI, 4871–9476) tons of sardine (Sardina pilchardus), 8800 (6195–12,647) tons of gadids, 1100 (721–1662) tons of hake (Merluccius merluccius) and 1900 (1222–2752) tons of scads (Trachurus sp.) annually. For striped dolphins (Stenella coeruleoalba), prey consumed were 900 (196–2661) tons of sardine, 6200 (3448–11,129) tons of gadids, 200 (11–504) tons of hake and 1600 (0–5318) tons of scads. Estimated amounts taken by harbour porpoises (Phocoena phocoena) and bottlenose dolphins (Tursiops truncatus) are much lower, reflecting their low abundance in the area. Cetacean predation on sardine represents 2–8% of the current M value, indicating that cetaceans probably have little influence on sardine population dynamics. For the southern hake stock, estimated average removal by cetaceans often exceeds M. While this may indicate that both M and the consumption estimates for hake require revision it also suggests that cetaceans could have a more significant impact on hake populations. Different approaches to estimation of energy requirements of cetaceans can result in figures that differ by at least a factor of 2. The lack of good estimates of field metabolic rate for most species probably represents the most serious barrier to reliably quantifying the role of cetaceans in the ecosystem.

Permanent Identifier: http://www.sciencedirect.com/science/article/pii/S0967064513003810

 

Author(s): Rudi Voss, Martin F. Quaas, Jörn O. Schmidt, Julia Hoffmann

Title: Regional trade-offs from multi-species maximum sustainable yield (MMSY) management options 

The maximum sustainable yield (MSY) is, theoretically, the largest yield that can be taken from a single species’ stock over an indefinite period. Formulation of strategic MSY management goals is, however, complicated by the need to move beyond biological single-species considerations. Interactions among species necessitate multispecies (MMSY) definitions, incorporating ecological, economic and social considerations. We developed an ecological? economic model of the Baltic Sea, simulating stock dynamics of interacting populations of cod Gadus morhua, herring Clupea harengus and sprat Sprattus sprattus. We investigated a set of different strategic management options. These likely, yet non-formalized experiments evaluate and illuminate alternative regional trade-offs. We computed multi-species maximum economic yield (MMEY) under certain eco logical constraints, with profits as a performance indicator. An unconstrained profit-maximizing management strategy would lead to a highly profitable cod fishery in a cod-dominated ecosystem. Concurrent sprat stock size (and profits) would be low, falling below ecological precautionary reference points. Consideration of ecological constraints on minimum stock sizes leaves a range of strategies, including the change from a cod-dominated to a more clupeiddominated system. The regional distribution of profits depends on the management. Therefore, adjustment payments or other forms of compensation might be needed to achieve a concordant agreement on strategic multi-species management goals.

Permanent Identifier: http://www.int-res.com/articles/feature/m498p001.pdf

 

Author(s): Rudi Voss , Martin F. Quaas, Jörn O. Schmidt, Olli Tahvonen, Martin Lindegren, Christian Möllmann

Title: Assessing Social – Ecological Trade-Offs to Advance Ecosystem-Based Fisheries Management 

Modern resource management faces trade-offs in the provision of various ecosystem goods and services to humanity. For fisheries management to develop into an ecosystem-based approach, the goal is not only to maximize economic profits, but to consider equally important conservation and social equity goals. We introduce such a triple-bottom line approach to the management of multi-species fisheries using the Baltic Sea as a case study. We apply a coupled ecological-economic optimization model to address the actual fisheries management challenge of trading-off the recovery of collapsed cod stocks versus the health of ecologically important forage fish populations. Management strategies based on profit maximization would rebuild the cod stock to high levels but may cause the risk of stock collapse for forage species with low market value, such as Baltic sprat (Fig. 1A ). Economically efficient conservation efforts to protect sprat would be borne almost exclusively by the forage fishery as sprat fishing effort and profits would strongly be reduced. Unless compensation is paid, this would challenge equity between fishing sectors (Fig. 1B). Optimizing equity while respecting sprat biomass precautionary levels would reduce potential profits of the overall Baltic fishery, but may offer an acceptable balance between overall profits, species conservation and social equity (Fig. 1C). Our case study shows a practical example of how an ecosystem-based fisheries management will be able to offer society options to solve common conflicts between different resource uses. Adding equity considerations to the traditional trade-off between economy and ecology will greatly enhance credibility and hence compliance to management decisions, a further footstep towards healthy fish stocks and sustainable fisheries in the world ocean.

Permanent Identifier: http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0107811 

 

Author(s): C. D. Maravelias, M. Pantazi and F. Maynou

Title: Fisheries management scenarios: trade-offs between economic and biological objectives

An age-structured, population biology submodel and an economic submodel with vessel-specific dynamics were applied to a demersal fishery in the North Aegean (NE Mediterranean) that consists of three main stocks: European hake Merluccius merluccius (L.), red mullet Mullus barbatus L. and striped red mullet Mullus surmuletus L. The Mefisto model is a bioeconomic simulation model through which the biological and economic submodels (disaggregated at the vessel level) are linked by means of a fishing mortality vector. Alternative management scenarios were built and tested based on input controls, and the performance of these strategies was examined against those of current policies. Three alternative management strategies were as follows: (1) reducing the coastal fisheries' fleet units; (2) limiting the effort level (days at sea) of the trawl fleets; and (3) changing the selectivity patterns of the trawl by increasing mesh size. The results show that for all three species, any of the three management measures (input controls) would be beneficial to both the stock and the fleets (over the medium and long terms) compared with the projections over time for the status quo. Improving the selectivity of the fishing gear proved to be more beneficial than limiting nominal effort, which was in turn more beneficial than decreasing coastal fleet size.

Permanent Identifier: http://onlinelibrary.wiley.com/doi/10.1111/fme.12060/abstract

  

Author(s): José-Maríá Da Rocha, Maríá-José Gutiérrez and Santiago Cerviño

Title: Reference Points Based on Dynamic Optimization: A Versatile Algorithm for Mixed Fishery Management with Bioeconomic Age-structured Models 

Single-species management objectives may not be consistent within mixed fisheries. They may lead species to unsafe situations,promote discarding of over-quota, and/or misreporting of catches. We provide an algorithm for characterizing bioeconomic reference points for a mixed fishery as the steady-state solution of a dynamic optimal management problem. The optimization problem takes into account that: (i) species are caught simultaneously in unselective fishing operations, and (ii) intertemporal discounting and fleet costs relate to reference points to discounted economic profits along optimal trajectories. We illustrate how the algorithm can be implemented by applying it to the European northern hake stock (Merluccius merluccius), where fleets also capture northern megrim (Lepidorhombus whiffiagonis) and northern anglerfish (Lophius piscatorius and Lophius budegassa). We find that optimal mixed management leads to a target reference point that is quite similar to two-thirds of the Fmsy single-species (hake) target. Mixed management is superior to single-species management because it leads the fishery to higher discounted profits, with higher long-term spawning-stock biomass for all species. We calculate that the lossesdue to the use of the Fmsy single-species (hake) target in this mixed fishery account for 11.4% of total discounted profits.

Permanent Identifier:  http://icesjms.oxfordjournals.org/content/early/2012/02/08/icesjms.fss012.short

 

Author(s): E. Van Leeuwen, Å. Brännström, V.A.A. Jansen, U. Dieckmann and A.G. Rossberg 

Title: A Generalized Functional Response for Predators that Switch Between Multiple Prey Species  

We develop a theory for the food intake of a predator that can switch between multiple prey species. The theory addresses empirical observations of prey switching and is based on the behavioural assumption that a predator tends to continue feeding on prey that are similar to the prey it has consumed last, in terms of, e.g., their morphology, defences, location, habitat choice, or behaviour. From a predator’s dietary history and the assumed similarity relationship among prey species, we de-rive a general closed-form multi-species functional response for describing predators switching be-tween multiple prey species. Our theory includes the Holling type II functional response as a special case and makes consistent predictions when populations of equivalent prey are aggregated or split. An analysis of the derived functional response enables us to highlight the following five main findings. (1) Prey switching leads to an approximate power-law relationship between ratios of prey abundance and prey intake, consistent with experimental data. (2) In agreement with empirical observations, the theory predicts an upper limit of 2 for the exponent of such power laws. (3) Our theory predicts devia-tions from power-law switching at very low and very high prey-abundance ratios. (4) The theory can predict the diet composition of a predator feeding on multiple prey species from diet observations for predators feeding only on pairs of prey species. (5) Predators foraging on more prey species will show less pronounced prey switching than predators foraging on fewer prey species, thus providing a natural explanation for the known difficulties of observing prey switching in the field.

Permanent Identifier:http://www.sciencedirect.com/science/article/pii/S0022519313000611

 

Author(s): Da Rocha J.M., Cerviño S., Villasante S.

Title: The Common Fisheries Policy: An enforcement problem 

Marine populations in Europe are in decline due to the unsuccessful results of the Common Fisheries Policy. By combining data of scientific recommendations from ICES, TACs approved and reported landings with an age-structured model, the objectives of this paper are to investigate the level of compliance of the TAC regulation, and the level of enforcement and its economic impact on fishery resources. The results presented here suggest that while there does not exist a regular pattern between TAC proposal and TAC approved, there is a clear pattern between TAC approved and reported landings. As a consequence, there is a regular lack of enforcement at national fisheries authority level. The paper also presents results of the recovery plans for the Southern hake and the Atlantic cod fisheries as case studies to illustrate the level of enforcement based on collusion between national fisheries advisers and industry. The results from both cases studies analyzed here indicate that drastic solutions could generate positive results for the recovery of the stocks, but perhaps they are not always the best measure in fisheries management due to the high economic losses for fishermen and social effects on coastal communities in the short and medium term. Finally, this work demonstrates that if the recovery plans had been implemented, the net present profits for both fisheries would have increased over time.

Permanent Identifier: http://www.sciencedirect.com/science/article/pii/S0308597X12000425

 

Author(s): Da Rocha J.M. and Gutiérrez M.J.

Title: Endogenous Fishery Management in a Stochastic Model: Why Do Fishery Agencies Use TACs Along with Fishing Periods?

This paper seeks to explain the circumstances under which using total allowable catch (TAC) as an instrument to manage a fishery along with fishing periods may be of interest from a regulatory point of view. The deterministic analysis by Homans and Wilen (J Environ Econ Manag 32:1–21, 1997) and Anderson (Ann Oper Res 94:231–257, 2000) is thus extended to a stochastic scenario where the resource cannot be measured accurately. The resulting model is solved numerically to find the optimal control rules in the Iberian sardine stock. Three relevant conclusions can be highlighted from simulations: first, the greater the uncertainty regarding the state of the stock, the lower the probability of the fishery being closed before the end of the fishing period. Second, the use of TACs as a management instrument in fisheries that are already regulated by fishing periods leads to: (i) an increase in the optimal season length and harvests, especially for medium and high numbers of licences; (ii) improved biological and economic variables when the fleet is large; and (iii) extinction risk for the resource being eliminated. Third, the regulator would rather select the number of licences than restrict the season length.

Permanent Identifier: http://www.springerlink.com/content/524247584nh87766/?MUD=MP

 

Author(s): Da Rocha J.M., Gutiérrez M.J. and Antelo L.T.

Title: Selectivity, Pulse Fishing and Endogenous Lifespan in Beverton-Holt Models 

Optimal management in a multi-cohort Beverton-Holt model with any number of age classes and imperfect selectivity is equivalent to finding the optimal fish lifespan by chosen fallow cycles. Optimal policy differs in two main ways from the optimal lifespan rule with perfect selectivity. First, weight gain is valued in terms of the whole population structure. Second, the cost of waiting is the interest rate adjusted for the increase in the pulse length. This point is especially relevant for assessing the role of selectivity. Imperfect selectivity reduces the optimal lifespan and the optimal pulse length. We illustrate our theoretical findings with a numerical example. Results obtained using global numerical methods select the optimal pulse length predicted by the optimal lifespan rule.

Permanent Identifier: http://www.springerlink.com/content/c7gq267n72270317/

 

Author(s): Da Rocha J.M., Gutiérrez M.J., Cerviño S., Antelo L.T.

Title: “logMSY” and optimal harvesting control rules: New tools for the implementation of the European Common Fisheries Policy 

The reform of the European Common Fisheries Policy (CFP) aims to restores and maintains fish resources at levels which can produce the maximum sustainable yield (MSY) not later than 2015. In this paper we show why if MSY is used as reference point, optimal management may entail pulse fishing. This means that current management of the European fisheries is based on metrics that may generate solutions that would not be accepted as feasible due to the large social costs implied. We discuss why changes in the metrics used to define the reference point (the logMSY) and/or optimal harvesting control rules that stabilize the employment and the biomass around the optimal stationary values are two possible solutions of this paradox. The European Union should take into account all these considerations for the CFP reform proposals.

Permanent Identifier: http://www.sciencedirect.com/science/article/pii/S0964569112001615  

 

Author(s): Fung T., Farnsworth K.D, Shephard S., Reid D.G., Rossberg A.G.

Title: Why the size structure of marine communities can require decades to recover from fishing 

A dynamic food-web model of more than 1000 species was used to quantify the recovery trajectory of marine community size-structure under different hypothetical fishing regimes, using the Northeast Atlantic as an example. Size-structure was summarised by four indicators: the Large Fish Indicator (LFI), the Large Species Indicator (LSI), the biomass-weighted mean maximum length of fish species (EMBED Equation.3) and the biomass-weighted mean maturation length of fish species (EMBED Equation.3). Time-series of these indicators recorded recovery following release from fishing with various size-selectivities, intensities and durations. In model simulations, fishing-induced trophic cascades were observed to distort fish community size-structure, but these did not have a large influence on recovery level or duration as measured by the four indicators. However, simulations showed that local extinctions of large fish species increased in number with both fishing intensity and duration, and could strongly limit the recovery level. Recovery of fish community size-structure to near equilibrium frequently took multiple decades in simulations; these long transient periods suggest that management interventions for size-structure recovery may require much longer than previously thought. Our results demonstrate the need for community-level modelling to set realistic targets for management of community size-structure.

Permanent Identifier: http://www.int-res.com/prepress/m10305.html

 

Author(s): Quaas M.F., Froese R., Herwartz H., Requate T., Schmidt J.O., Voss R.

Title: Fishing industry borrows from natural capital at high shadow interest rates 

Fish stocks can be considered as natural capital stocks providing harvestable fish. Fishing at low stock sizes means borrowing from the natural asset. While fishing a particular quantity generates immediate profits and income, an interest rate has to be paid in terms of foregone future fishing income, as the fish stock's reproductive capacity remains low and fishing costs stay high. In this paper we propose to apply the concept of shadow interest rate to quantify the degree of overfishing. It incorporates the relevant biological and economic information and compares across fish stocks. We calculate the shadow interest rates for 13 major European fish stocks and find these rates to range from 10% to more than 200%. The concept of the shadow interest rate can be used to make the economic consequences of overfishing transparent and to evaluate the profitability of short-term catch reductions as investments in natural capital stocks.

Permanent Identifier:http://www.sciencedirect.com/science/article/pii/S0921800912003072

 

Author(s): Shephard S., Fung T., Rossberg A.G., Farnsworth K.D., Reid D.G., Greenstreet S.P.R., Warnes S.

Title: Modelling recovery of Celtic Sea demersal fish community size-structure

The Large Fish Indicator (LFI) is a size-based indicator of fish community state. The indicator describes the proportion by biomass of a fish community represented by fish larger than some size threshold. From an observed peak value of 0.49 in 1990, the Celtic Sea LFI declined until about 2000 and then fluctuated around 0.10 throughout the 2000s. This decline in the LFI reflected a period of diminishing ‘large’ fish biomass, probably related to high levels of size selective fishing. During the study period, fishing mortality was maintained at consistently high values. Average biomass of ‘small’ fish fluctuated across the whole time series, showing a weak positive trend in recent years. Inter-annual variation in the LFI was increasingly driven by fluctuation in small fish biomass as large fish biomass declined. Simulations using a size-based ecosystem model suggested that recovery in Celtic Sea fish community size-structure (LFI) could demand at least 20% reductions in fishing pressure and occur on decadal timescales.

Permanent Identifier: http://www.sciencedirect.com/science/article/pii/S0165783612003542

 

Author(s): Shephard S., Gerritsen H., Kaiser M.J., Reid D.G.

Title: Spatial Heterogeneity in Fishing Creates de facto Refugia for Endangered Celtic Sea Elasmobranchs

The life history characteristics of some elasmobranchs make them particularly vulnerable to fishing mortality; about a third of all species are listed by the IUCN as Threatened or Near Threatened. Marine Protected Areas (MPAs) have been suggested as a tool for conservation of elasmobranchs, but they are likely to be effective only if such populations respond to fishing impacts at spatial-scales corresponding to MPA size. Using the example of the Celtic Sea, we modelled elasmobranch biomass (kg h21) in fisheries-independent survey hauls as a function of environmental variables and ‘local’ (within 20 km radius) fishing effort (h y21) recorded from Vessel Monitoring Systems data. Model selection using AIC suggested strongest support for linear mixed effects models in which the variables (i) fishing effort, (ii) geographic location and (iii) demersal fish assemblage had approximately equal importance in explaining elasmobranch biomass. In the eastern Celtic Sea, sampling sites that occurred in the lowest 10% of the observed fishing effort range recorded 10 species of elasmobranch including the critically endangered Dipturus spp. The most intensely fished 10% of sites had only three elasmobranch species, with two IUCN listed as Least Concern. Our results suggest that stable spatial heterogeneity in fishing effort creates de facto refugia for elasmobranchs in the Celtic Sea. However, changes in the present fisheries management regime could impair the refuge effect by changing fisher’s behaviour and displacing effort into these areas.

Permanent Identifier: http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0049307

 

Author(s): Christian Möllmann, Martin Lindegren, Thorsten Blenckner, Lena Bergström, Michele Casini, Rabea Diekmann, Juha Flinkman, Bärbel Müller-Karulis, Stefan Neuenfeldt, Jörn O. Schmidt, Maciej Tomczak, Rüdiger Voss and Anna Gårdmark

Title: Implementing ecosystem-based fisheries management: from single-species to integrated ecosystem assessment and advice for Baltic Sea fish stocks 

Theory behind ecosystem-based management (EBM) and ecosystem-based fisheries management (EBFM) is now well developed. However, the implementation of EBFM exemplified by fisheries management in Europe is still largely based on single-species assessments and ignores the wider ecosystem context and impact. The reason for the lack or slow implementation of EBM and specifically EBFM is a lack of a coherent strategy. Such a strategy is offered by recently developed integrated ecosystem assessments (IEAs), a formal synthesis tool to quantitatively analyse information on relevant natural and socio-economic factors, in relation to specified management objectives. Here, we focus on implementing the IEA approach for Baltic Sea fish stocks. We combine both tactical and strategic management aspects into a single strategy that supports the present Baltic Sea fish stock advice, conducted by the International Council for the Exploration of the Sea (ICES). We first review the state of the art in the development of IEA within the current management framework. We then outline and discuss an approach that integrates fish stock advice and IEAs for the Baltic Sea. We intentionally focus on the central Baltic Sea and its three major fish stocks cod (Gadus morhua), herring (Clupea harengus), and sprat (Sprattus sprattus), but emphasize that our approach may be applied to other parts and stocks of the Baltic, as well as other ocean areas. 

Permanent Identifier: http://icesjms.oxfordjournals.org/content/early/2013/08/24/icesjms.fst123

 

Author(s): Skagen, D. W., Skern-Mauritzen, M., Dankel, D., Enberg, K., Kjesbu, O. S., and Nash, R. D. M.

Title: A simulation framework for evaluating fisheries management decisions using environmental information 

The population dynamics of marine fish stocks are influenced by both physical and biological conditions. Yet, such environmental impacts on stock dynamics, and hence stock production, are rarely included in applied fisheries management. To test the utility of taking ecosystem information into account in management decisions requires efficient tools. We propose a simulation framework for evaluating fisheries management schemes that use environmental information as part of the decision basis. A key feature is to link environmental signals to parameters in functions that define the population dynamics. This allows a direct incorporation of environmental drivers into models of population dynamic processes and emphasizes the need for a quantitative understanding of the influence of environmental drivers on such processes. The utility of the simulation framework is demonstrated through a worked example with different management scenarios, where decisions to increase or decrease the exploitation rely on environmental indicators only, or also on information on stock abundance. In this example, a management that was based on indicators only, without updated measures of the state of the stock itself, failed to respond adequately to changes in stock productivity.

Permanent Identifier: http://icesjms.oxfordjournals.org/content/70/4/743.abstract

 

Author(s): Da Rocha, J. M., Gutiérrez, M. J., Antelo, L. T.

Title: Pulse vs. optimal stationary fishing: The Northern Stock of Hake

Pulse fishing may be a global optimal strategy in multicohort fisheries. In this article we compare pulse fishing solutions obtained by using global numerical methods with the analytical stationary optimal solution. This allows us to quantify the potential benefits associated with the use of periodic fishing in the Northern Stock of Hake. Results show first that management plans based exclusively on traditional reference targets such as Fmsy may drive economic results for fisheries far away from the optimal; second, that global optimal solutions would imply the cyclical closure of fisheries for some periods; and third, that second best stationary policies with stable employment only reduce the optimal present value of discounted profit by 2%.

Permanent Identifier: http://www.sciencedirect.com/science/article/pii/S0165783612000409

 

Author(s): Garcia, D., Prellezo, R., Sanchez, S., Andres, M., Santurtun, M.

Title: FLBEIA: A toolbox to conduct Bio-Economic Impact Assessment of fisheries management strategies

FLBEIA is an R library which provides a flexible and generic tool to conduct BioEconomic Impact Assessment of fisheries management strategies. It has been built under a Management Strategy Evaluation framework which consist in simulating the fisheries system together with the management process. The fisheries system is simulated in the so called Operating Model which describes the true dynamics of the system and the management process is simulated in the Management Procedure which generates an observed system from the reality. The management advice is generated based on the observed system, instead of on the real one.

The model is multistock, multifleet, seasonal and uncertainty is introduced by means of montecarlo simulation. In addition, it has a covariables component that allows introducing variables of interest not present in biological and fleets components. For example, it could be used to introduce relevant ecosystem components in a simple way. FLBEIA represents a middle way between complicated whole ecosystem models and simple bioeconomic fisheries models.

The fishery system and management process are divided in low level interlinked processes, providing the library one or several models to describe each of the process. The user chooses the models to be used in each specific model implementation and if the functions provided within FLBEIA do not fulfill the requirements for some of the components, the user can code the functions that adequately describe the dynamics of those processes and use the existing ones for the rest.

In this paper we present FLBEIA library describing how fishery system and management process are modeled, the low level process that build up the model and the available functions to model them, the necessary data and its form to condition the model and its principal advantages and limitations. Finally, we briefly present its application to 3 different case studies, Seabream artisanal fisheries in the Gulf of Cádiz, French deep-watter mixed-fisheries and Basque inshore sequential- fisheries

Permanent Identifier: http://www.azti.es/mailings/flbeia/Garcia_et_al_2012_ASCICESCMK01.pdf

 

Author(s): van Leeuwena, E., Brännströmb, Å., Jansena, V.A.A., Dieckmannc, U., Rossberg, A.G.

Title: A generalized functional response for predators that switch between multiple prey species.

We develop a theory for the food intake of a predator that can switch between multiple prey species. The theory addresses empirical observations of prey switching and is based on the behavioural assumption that a predator tends to continue feeding on prey that are similar to the prey it has consumed last, in terms of, e.g., their morphology, defences, location, habitat choice, or behaviour. From a predator’s dietary history and the assumed similarity relationship among prey species, we derive a general closed-form multi-species functional response for describing predators switching between multiple prey species. Our theory includes the Holling type II functional response as a special case and makes consistent predictions when populations of equivalent prey are aggregated or split. An analysis of the derived functional response enables us to highlight the following five main findings. (1) Prey switching leads to an approximate power-law relationship between ratios of prey abundance and prey intake, consistent with experimental data. (2) In agreement with empirical observations, the theory predicts an upper limit of 2 for the exponent of such power laws. (3) Our theory predicts deviations from power-law switching at very low and very high prey-abundance ratios. (4) The theory can predict the diet composition of a predator feeding on multiple prey species from diet observations for predators feeding only on pairs of prey species. (5) Predators foraging on more prey species will show less pronounced prey switching than predators foraging on fewer prey species, thus providing a natural explanation for the known difficulties of observing prey switching in the field.

Permanent Identifier: http://www.sciencedirect.com/science/article/pii/S0022519313000611

 

Author(s): Jacobsen, N. S., Gislason, H., Andersen, K. H.

Title: The consequences of balanced harvesting of fish communities

Balanced harvesting, where species or individuals are exploited in accordance with their productivity, has been proposed as a way to minimize the effects of fishing on marine fish communities and ecosystems. This calls for a thorough examination of the consequences balanced harvesting has on fish community structure and yield. We use a size- and trait-based model that resolves individual interactions through competition and predation to compare balanced harvesting with traditional selective harvesting, which protects juvenile fish from fishing. Four different exploitation patterns, generated by combining selective or unselective harvesting with balanced or unbalanced fishing, are compared. We find that unselective balanced fishing, where individuals are exploited in proportion to their productivity, produces a slightly larger total maximum sustainable yield than the other exploitation patterns and, for a given yield, the least change in the relative biomass composition of the fish community. Because fishing reduces competition, predation and cannibalism within the community, the total maximum sustainable yield is achieved at high exploitation rates. The yield from unselective balanced fishing is dominated by small individuals, whereas selective fishing produces a much higher proportion of large individuals in the yield. Although unselective balanced fishing is predicted to produce the highest total maximum sustainable yield and the lowest impact on trophic structure, it is effectively a fishery predominantly targeting small forage fish.

Permanent Identifier: http://rspb.royalsocietypublishing.org/content/281/1775/20132701

 

Author(s): Heino, M., Baulier, L., Boukal, D. S., Ernande, B., Johnston, F. D., Mollet, F. M., Pardoe, H., Therkildsen, N. O., Uusi-Heikkilä, S., Vainikka, A., Arlinghaus, R., Dankel, D. J., Dunlop, E. S., Eikeset, A. M., Enberg, K., Engelhard G. H., Jørgensen, C., Laugen, A. T., Matsumura, S., Nusslé, S., Urbach, D., Whitlock, R., Rijnsdorp, A. D., and Dieckmann, U.

Title: Can fisheries-induced evolution shift reference points for fisheries management?

Biological reference points are important tools for fisheries management. Reference points are not static, but may change when a population's environment or the population itself changes. Fisheries-induced evolution is one mechanism that can alter population characteristics, leading to “shifting” reference points by modifying the underlying biological processes or by changing the perception of a fishery system. The former causes changes in “true” reference points, whereas the latter is caused by changes in the yardsticks used to quantify a system's status. Unaccounted shifts of either kind imply that reference points gradually lose their intended meaning. This can lead to increased precaution, which is safe, but potentially costly. Shifts can also occur in more perilous directions, such that actual risks are greater than anticipated. Our qualitative analysis suggests that all commonly used reference points are susceptible to shifting through fisheries-induced evolution, including the limit and “precautionary” reference points for spawning-stock biomass, Blim and Bpa, and the target reference point for fishing mortality, F0.1. Our findings call for increased awareness of fisheries-induced changes and highlight the value of always basing reference points on adequately updated information, to capture all changes in the biological processes that drive fish population dynamics.

Permanent Identifier: http://icesjms.oxfordjournals.org/content/70/4/707.abstract

 

Author(s): Santos, M.B., Saavedra, C., Pierce, G.J.

Title: Quantifying the predation on sardine and hake by cetaceans in the Atlantic waters of the Iberian peninsula

Construction of ecosystem models requires detailed information on trophic interactions which may not be readily available, especially for top predators such as cetaceans. Such information can also be useful to estimate natural mortality (M) for fish stock assessments and to evaluate the potential for competition between cetaceans and fisheries. In the present paper we provide estimates and confidence limits, taking into account sampling error, for consumption of fish by the four most common cetaceans along the Atlantic coast of the Iberian Peninsula, while highlighting the uncertainties and biases inherent in the information presently available on energy requirements, diet and population size. We estimated that common dolphins (Delphinus delphis) consume around 6800 (95% CI, 4871–9476) tons of sardine (Sardina pilchardus), 8800 (6195–12,647) tons of gadids, 1100 (721–1662) tons of hake (Merluccius merluccius) and 1900 (1222–2752) tons of scads (Trachurus sp.) annually. For striped dolphins (Stenella coeruleoalba), prey consumed were 900 (196–2661) tons of sardine, 6200 (3448–11,129) tons of gadids, 200 (11–504) tons of hake and 1600 (0–5318) tons of scads. Estimated amounts taken by harbour porpoises (Phocoena phocoena) and bottlenose dolphins (Tursiops truncatus) are much lower, reflecting their low abundance in the area. Cetacean predation on sardine represents 2–8% of the current M value, indicating that cetaceans probably have little influence on sardine population dynamics. For the southern hake stock, estimated average removal by cetaceans often exceeds M. While this may indicate that both M and the consumption estimates for hake require revision it also suggests that cetaceans could have a more significant impact on hake populations. Different approaches to estimation of energy requirements of cetaceans can result in figures that differ by at least a factor of 2. The lack of good estimates of field metabolic rate for most species probably represents the most serious barrier to reliably quantifying the role of cetaceans in the ecosystem.

Permanent Identifier: http://www.sciencedirect.com/science/article/pii/S0967064513003810

 

Author(s): Drouineau, H., Dumoulin, N., Lambert, P., Mahévas, S., Picheny, V., Rouan, L., Soulié, J.C.

Title: Restitution du séminaire Optimisation - Modèle Complexe

La modélisation est fortement utilisée pour renforcer la compréhension du fonctionnement des systèmes complexes et aider à la prise de décision dans un environnement dynamique incertain. Le bon usage de ces modèles, le plus souvent complexes pour reproduire au plus juste le système étudié, requiert le respect de bonnes pratiques adhoc de modélisation à défaut d’avoir une méthodologie formalisée. Il s'agit en tout premier lieu de la transparence dans le processus de construction et de la validation du modèle. Dans le cadre du réseau Mexico, nous avons largement exploré les approches basées sur les analyses de sensibilité globale pour faciliter le développement, l'utilisation des modèles et la validation de ces derniers dans un processus de co-construction avec les experts thématiciens. Cette famille de méthodes permet d'identifier et hiérarchiser les paramètres clés qui, dès lors, doivent être estimés (calibrés) avec précision pour garantir un bon contrôle des sorties du modèle. L'optimisation est un champ de méthodes mathématiques cherchant à analyser et à résoudre analytiquement ou numériquement les problèmes qui consistent à déterminer le meilleur élément d'un ensemble, au sens d'un ou plusieurs critères quantitatifs donnés et de contraintes. Elle permet d'appréhender la calibration des modèles, la recherche d'une décision optimale selon un ou plusieurs critères prédits par le modèle, etc. En fait toute classe de problèmes modélisables peut conduire à un problème d'optimisation, pourvu que l'on y introduise des paramètres ou variables à optimiser. La principale difficulté de l’exercice d’optimisation vient du fait que les modèles complexes que nous appréhendons sont bien souvent non linéaires et non dérivables. La problématique de ce séminaire se concentre autour de l'optimisation de la paramétrisation d'un modèle complexe qui présente au moins une des caractéristiques suivantes (une boîte noire, un code de calcul long ou coûteux, de nombreux paramètres continus ou discrets, de multiples variables de sortie et des processus déterministes ou stochastiques). L'optimisation visera à trouver i) les valeurs des paramètres permettant de reproduire au mieux les observations du système modélisé ou ii) les valeurs de variables décisionnelles (discrètes ou continues) permettant de remplir certains critères, le tout en respectant un ensemble de contraintes préalablement définies.

Permanent Identifier: http://reseau-mexico.fr/sites/reseau-mexico.fr/files/BookSynth%C3%A8seJanv2015.pdf

 

Author(s): Voss, R., Quaas, M. F., Schmidt, J. O., Tahvonen, O., Lindegren, M., Möllmann, C.

Title: Assessing Social – Ecological Trade-Offs to Advance Ecosystem-Based Fisheries Management

Modern resource management faces trade-offs in the provision of various ecosystem goods and services to humanity. For fisheries management to develop into an ecosystem-based approach, the goal is not only to maximize economic profits, but to consider equally important conservation and social equity goals. We introduce such a triple-bottom line approach to the management of multi-species fisheries using the Baltic Sea as a case study. We apply a coupled ecological-economic optimization model to address the actual fisheries management challenge of trading-off the recovery of collapsed cod stocks versus the health of ecologically important forage fish populations. Management strategies based on profit maximization would rebuild the cod stock to high levels but may cause the risk of stock collapse for forage species with low market value, such as Baltic sprat (Fig. 1A). Economically efficient conservation efforts to protect sprat would be borne almost exclusively by the forage fishery as sprat fishing effort and profits would strongly be reduced. Unless compensation is paid, this would challenge equity between fishing sectors (Fig. 1B). Optimizing equity while respecting sprat biomass precautionary levels would reduce potential profits of the overall Baltic fishery, but may offer an acceptable balance between overall profits, species conservation and social equity (Fig. 1C). Our case study shows a practical example of how an ecosystem-based fisheries management will be able to offer society options to solve common conflicts between different resource uses. Adding equity considerations to the traditional trade-off between economy and ecology will greatly enhance credibility and hence compliance to management decisions, a further footstep towards healthy fish stocks and sustainable fisheries in the world ocean.

Permanent Identifier: http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0107811

 

Author(s): Merino, G., Murua, H., Arrizabalaga, H., Santiago, J.

Title: Assessing Social – Ecological Trade-Offs to Advance Ecosystem-Based Fisheries Management

The Indian Ocean (IO) is an area of great commercial interest for European fishing industries. Among others, European fleets target bigeye, yellowfin and skipjack, three tuna species that conform the known as tropical tuna fisheries in the IO. These species inhabit international and national jurisdiction waters, which makes them prone for their collective management through Regional Fisheries Management Organizations (RFMO). The Indian Ocean Tuna Commission (IOTC) is an intergovernmental organization responsible for the management of tuna and tunalike species in the IO. The Commission has among other functions, responsibilities on (1) data collection, (2) research coordination, (3) the adoption of conservation and management measures to ensure the conservation of fish stocks and to promote their optimal utilization, and (4) consider socioeconomic aspects of fisheries considering the interests of developing coastal States. Within IOTC, the Maximum Sustainable Yield (MSY) has been used as a recommended target reference point for the tropical tuna fisheries. MyFISH aims to investigate a series of alternative target reference points in order to satisfy management preferences from stakeholders through numerical modelling and, interviews with interested parties in order to show their view on the challenges and potential solutions for the management of fisheries.

Following the structure of the project, this study is based on the MSY variants proposed in the Widely Ranging Regional Fisheries Advisory Council (RFMO) in the kick-off workshop in Vigo in April 2012. This information has been used to (1) define variants, constraints and to develop a numerical model framework, which has been used to (2) evaluate these variants, producing output in the form of a Decision Support Table (DST); finally, we discussed alternative ways to (3) implement the MSY variants in order to most effectively improve fisheries’ performance and respect management constraints.

Permanent Identifier: http://www.iotc.org/sites/default/files/documents/2014/11/IOTC-2014-WPTT16-52_-_MyFISH.pdf

 

Author(s): Merino, G., Quetglas, A., Maynou, F., Garau, A., Arrizabalaga, H., Murua, H., Santiago, J., Barange, M., Prellezo, R., García, D., Lleonart, J., Tserpes, G., XMaravelias, C., Carvalho, N., Austen, M., Fernandes, J. A., Oliver, P., Grau, A. M.

Title: Improving the performance of a Mediterranean demersal fishery toward economic objectives beyond MSY

Mediterranean demersal fisheries are highly multispecific and many of their target stocks are overexploited. In addition, rocketing fuel costs and low market prices of traditionally high-value species are challenging the viability of fisheries. Here, based on the numeric results of a simulation model, we conclude that this situation can be remedied by reducing both fishing mortality and fishing costs. According to our model results, fishing effort reductions of 48–71% would improve the health of fish stocks while increasing the economic profits of Mallorca islands bottom trawl fishery to as much as 1.9 M€ (146% higher than current profits). If all fish stocks were exploited at their MSY (or below) level, the reduction in fishing effort would have to be of 71% from current values. If equilibrium profits from the fishery were to be maximized (MEY), fishing effort would need to be reduced by 48%. These results must be taken with caution due the many sources of uncertainty of our analysis. The modeling tools used to estimate these values are conditional to the adequate treatment of two sources of uncertainty that are particularly problematic in Mediterranean fisheries: insufficiently known recruitment variability and lack of periodic evaluations of the state of many species. Our results show that fishing effort reductions would produce economic yield gains after a period of transition. Further studies on the benefits of changing the size-selection pattern of fisheries, on better estimation of stock–recruitment relationships and on better quantifications of the contribution of secondary species to these fisheries, are expected to improve the scientific recommendations for Mediterranean demersal fisheries toward sustainability principles.

Permanent Identifier: http://www.sciencedirect.com/science/article/pii/S0165783614001982

 

Author(s): Blenckner, T., Llope, M., Möllmann, C., Voss, R., Quaas, M. F., Casini, M., Lindegren, M., Folke, C., Stenseth, N. C.

Title: Climate and fishing steer ecosystem regeneration to uncertain economic futures

Overfishing of large predatory fish populations has resulted in lasting restructurings of entire marine food webs worldwide, with serious socio-economic consequences. Fortunately, some degraded ecosystems show signs of recovery. A key challenge for ecosystem management is to anticipate the degree to which recovery is possible. By applying a statistical food-web model, using the Baltic Sea as a case study, we show that under current temperature and salinity conditions, complete recovery of this heavily altered ecosystem will be impossible. Instead, the ecosystem regenerates towards a new ecological baseline. This new baseline is characterized by lower and more variable biomass of cod, the commercially most important fish stock in the Baltic Sea, even under very low exploitation pressure. Furthermore, a socio-economic assessment shows that this signal is amplified at the level of societal costs, owing to increased uncertainty in biomass and reduced consumer surplus. Specifically, the combined economic losses amount to approximately 120 million € per year, which equals half of today's maximum economic yield for the Baltic cod fishery. Our analyses suggest that shifts in ecological and economic baselines can lead to higher economic uncertainty and costs for exploited ecosystems, in particular, under climate change.

Permanent Identifier: http://rspb.royalsocietypublishing.org/content/282/1803/20142809

 

Author(s): Farcas, A., Rossberg, A. G.

Title: Maximum sustainable yield from interacting fish stocks in an uncertain world: two policy choices and underlying trade-offs

The case of fisheries management illustrates how the inherent structural instability of ecosystems can have deep-running policy implications. We contrast ten types of management plans to achieve maximum sustainable yields (MSY) from multiple stocks and compare their effectiveness based on a management strategy evaluation (MSE) that uses complex food webs in its operating model. Plans that primarily target specific stock sizes (BMSY) consistently led to higher yields than plans targeting specific fishing pressures (FMSY). A new type of self-optimising control rule, introduced here for its robustness to structural instability, led to intermediate yields. Plans to "maximise the yield from each stock separately", in the sense of a Nash equilibrium, produced total yields comparable to plans aiming to maximise total harvested biomass, but were more robust to structural instability. Most plans outperformed single-species management plans that set pressure targets without explicitly considering ecological interactions. Our analyses highlight trade-offs between yields, amiability to fair negotiations, pressures on biodiversity, and continuity with current approaches in the European context. Based on these results, we recommend directions for future developments of EU fisheries policy.

Permanent Identifier: http://arxiv.org/abs/1412.0199

 

Author(s): Da Rocha, J. M. & Gutiérrez, M. J.

Title: Lessons from the long-term management plan for northern hake: could the economic assessment have accepted it?

An economic working group was convened by the EU's Scientific, Technical and Economic Committee for Fisheries (STECF) in 2007 to evaluate the potential economic consequences of the long-term management plan for the northern hake (Merluccius merluccius) stock. An analysis of all the scenarios proposed by the biological assessment using the Economic Interpretation of ACFM Advice (EIAA) model showed that F at the status quo level was the best policy for both yield and profits, in terms of net present values. This result is counter-intuitive because it seems to suggest that effort costs do not influence economic indicators, whereas it is widely accepted that including costs negatively affects economic indicators. A dynamic age-structured model is applied to northern hake and shows that the optimal fishing mortality that maximizes the net present value of profits is <Fmax. The reason why the EIAA analysis was biased towards scenarios with F > Fmax is also shown.

Permanent Identifier: http://icesjms.oxfordjournals.org/content/early/2011/07/25/icesjms.fsr105.full

 

Author(s): Raúl Prellezoa and Richard Curtin

Title: Confronting the implementation of marine ecosystem-based management within the Common Fisheries Policy reform 

This paper confronts, by meta-synthesis of the literature, the definition of ecosystem-based management provided in the reform of the European Common Fisheries Policy (CFP) with the specific measures and the institutional framework foreseen in it.

By analysing the reform of the CFP by means of the ecosystem-based management framework, we conclude that there is a lack of instruments to deal with the social sustainability objective while economic and ecological sustainability could be simultaneously achieved with the specific measures considered in the reform.

Individually analysed, the specific measures could further benefit ecosystem-based management implementation, although not all the observed or analysed consequences of the implementation of these measures move in this direction. In that sense we conclude that the success of the ecosystem based management of EU fisheries depends much more on the specific implementation of the measures and on the accompanying incentives, which in the end, implies that the institutional and political settings will determine its success.

Permanent Identifier: http://www.sciencedirect.com/science/article/pii/S0964569115000691

 

Author(s): José María Da Rocha, Sebastián Villasante, and Rafael Trelles González

Title: Credible enforcement policies under illegal fishing: does individual transferable quotas induce to reduce the gap between approved and proposed allowable catches?

In general, approved Total Allowable Catches (TACs) are higher than proposed TACs by the scientific assessment and reported landings approved are higher than approved TAC. We build a simple enforcement agency’s behavior model that generates—as a rational behavior—those two facts. The model has two ingredients. First, there exists illegal fishing generated by an imperfect enforcement technology; second, the enforcement agency cannot commit on announced penalties. We show that lack of commitment increases the potential benefits for national enforcement agency of deviating from proposal (scientific optimal) quotas. Although the enforcement agency wants to announce a low quota target to induce a low level of illegal harvest, it will find optimal to revise the quota announced in order to reduce penalties and improve fishermen welfare. Therefore, agencies find it optimal to approve higher quotas than that proposed by the scientific advice. Our main result is to show that when full compliance is not possible, and national agencies cannot commit, the introduction of Individual Transferable Quotas increases the potential benefits for agencies of deviating from the optimal proposed TAC by the scientific advised.

Permanent Identifier: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3824872/

flagsThe research leading to these results has received funding from the European Union’s Seventh Framework Programme (FP7 /2007-2013) under grant agreement no 289257. This publication reflects the views only of the author, and the European Union cannot be held responsible for any use which maybe made of the information contained therein.