Evaluation and implementation of discards policies under catch-based fisheries management regimes

This thesis brings a contribution to the debate, formally recognising fishers as an integral part of the ecosystem, by investigating the implications of applying a policy of limiting discards at sea in complex mixed fisheries that are managed under catch limits for the well-being of both the ecosystem and humans. Discard restrictions and discard management regimes have been implemented to different extents in a number of fisheries around the world (e.g., Chile, Norway, Faroe Islands, Iceland, New Zealand, Namibia, Canada, and the US). The implementation, monitoring and control of the landing obligation generates some new challenges. In particular, the focus of monitoring and control shifts from landing to activities at sea leading to potentially higher costs of enforcement as it might require, for successful implementation, full observer coverage or electronic video monitoring to validate a self-reporting system. In chapter 2, experiences from fisheries around the world show that choosing the right measures is not a simple process and therefore, management authorities need to simultaneously implement complementary measures which will support implementation and encourage compliance with discarding rules. The need to adapt the regulatory framework does not just concern enforcement systems. Other measures, including adaptations to the technical measure’s framework, also need to be considered. Improved selectivity of fishing gears remains a primary and important tool to avoid discards. In chapter 3 I studied the selective properties of a bottom trawl fitted with a 70 mm diamond mesh codend and a 100 mm top square mesh panel (SMP) in the commercial Basque bottom otter trawlers in the Bay of Biscay. Results suggested that a 100 mm SMP potentially enable undersized and immature individuals to escape through the meshes. However, the selectivity cruises demonstrated that in practice, the SMP was largely ineffective at releasing undersized and the release potential for the diamond mesh codend was found to be significantly lower than the length-at-maturity and the legal minimum conservation reference size for hake, pouting and red mullet. The introduction of the obligation to land all catches will create new challenges for this trawl fleet and thereby an incentive to improve selectivity to avoid unwanted catches of undersized individuals. Moving to using more selective gears (bigger mesh size codend) may provide a partial solution to mitigate the potential impact of the landing obligation. However, such a measure may also lead to losses in marketable catch and reductions in revenue that make the fishery unviable in the short-term and perhaps in the long-term. Hence, dynamic state variable models allow studying how fishers may respond to changing policies and what consequences this adaptive response may have for the economic and social performance of the fishery. The model results suggested that these negative short-term impacts could be alleviated by incorporation of inter-species quota flexibility in the implementation of the landing obligation. The results indicate that there will be a strong incentive to use this policy arrangement to alleviate the choke effect problem where species with limiting quotas constrain the fishery. To study the possible consequences on a longer time horizon, an MSE approach can be applied to evaluate the long-term consequences of the changes in exploitation pattern on the productivity of the exploited stocks. Combining the main CFP objectives: exploiting at MSY and no discarding allowance, the MSE showed that quota species brought risk of changing exploitation patterns also for non-quota stocks. Fishing effort was constrained by one or two quota stocks, resulting in drastic reductions of effort over the short-term and mid-term.</p

a4a short research project - Studying spatial effects on stock dynamics of North Sea cod and plaice in the Skagerrak

Under the scope of the a4a Initiative, the JRC is promoting cooperative activities between fisheries scientists with the aim to test, disseminate and promote a4a methods. These Small Research Projects (SRP) are focused on (i) comparing the a4a statistical catch-at- age model with results from other assessment models, and (ii) exploring research questions using case studies. The Workshop dedicated to the North Sea took place in Ispra, Italy, the 1st to the 5th of December. The main objectives were to study spatial effects on stock dynamics through the use of stock assessment models. The terms of reference of the workshop were: 1. Use the a4a stock assessment framework to study spatial effects on stock dynamics; 2. Apply the methodology to the stocks of cod in the North Sea and plaice in the Skagerrak. 3. Report to STECF and other relevant management bodies.JRC.G.3-Maritime affair

Likely status and changes in the main economic and fishery indicators under the landing obligation : A case study of the Basque trawl fishery

We modelled fleet dynamics and the economic impact of three implementations of the EU landing obligation for fisheries, and contrasted the results with those obtained under a scenario of no landing obligation. Simulations were performed using a dynamic state variable model of effort allocation for the Basque trawl fleet, assuming that the landing obligation had been implemented in 2012. The three implementations of the landing obligation involved different policy arrangements: (i) quota increases; (ii) international swapping of quotas; and (iii) inter-species quota flexibility. All three scenarios resulted in changes to fishing patterns caused by choke species and improved selectivity of harvest, but also resulted in a negative short-term impact on the economic performance of the fleet. We report average reductions in net revenue of up to 60% when compared with results obtained under a no landing obligation scenario. Our model results suggested that these negative short-term impacts could be alleviated by incorporation of inter-species quota flexibility in the implementation of the landing obligation. Our results indicate that there will be a strong incentive to use this policy arrangement to alleviate the choke effect problem where species with limiting quotas constrain the fishery

Likely status and changes in the main economic and fishery indicators under the landing obligation: A case study of the Basque trawl fishery

We modelled fleet dynamics and the economic impact of three implementations of the EU landing obligation for fisheries, and contrasted the results with those obtained under a scenario of no landing obligation. Simulations were performed using a dynamic state variable model of effort allocation for the Basque trawl fleet, assuming that the landing obligation had been implemented in 2012. The three implementations of the landing obligation involved different policy arrangements: (i) quota increases; (ii) international swapping of quotas; and (iii) interspecies quota flexibility. All three scenarios resulted in changes to fishing patterns caused by choke species and improved selectivity of harvest, but also resulted in a negative short-term impact on the economic performance of the fleet. We report average reductions in net revenue of up to 60% when compared with results obtained under a no landing obligation scenario. Our model results suggested that these negative short-term impacts could be alleviated by incorporation of inter-species quota flexibility in the implementation of the landing obligation. Our results indicate that there will be a strong incentive to use this policy arrangement to alleviate the choke effect problem where species with limiting quotas constrain the fishery.JRC.E.6-Demography, Migration and Governanc

Initial draft: Model and Simulation framework of the BoB mixed fishery, including the economic and operational factors

The reform of the Common Fisheries Policy (CFP) has introduced a landings obligation to end the practice of discarding at sea. The ecological and economic effects of these landings obligations are unknown for many mixed fisheries. It seems likely, though, that fishing fleets will adaptively respond to the new policy, trying to sustain viable fisheries under the new policy constraints. Here, we present a methodology to project the effects of the landings obligation on the sustainability and profitability of mixed fisheries under quota management using a dynamic state variable model. The adaptive response of the fleets to different implementation scenarios will be mimicked evaluating some scenarios that include: (i) a complete discards ban, and (ii) a combination of de minimis and inter-species flexibility in quota use. These scenarios will be compared with the results of maintaining a policy permitting all discards. The final comparison across alternative discard management regimes will look at both the ecological and economic indicators. The Basque trawl mixed fishery on the Bay of Biscay is used as case study.JRC.G.3-Maritime affair

Review of discards management regimes

Current European fisheries management is changing rapidly, aiming towards implementation of an “Ecosystem Approach to Fisheries” in which maximum sustainable yields is maintained for all commercially important fish stocks. Such a maximum sustainable yield is conceptually trivial when species are considered in isolation. However, when ecosystem effects such as competition and predation are accounted for, trade-offs between socio-economic factors and ecosystem functioning occur, dependent on management choices. In addition, fishing vessels will be obliged to land all fish caught, banning “discarding” of fish. The recent discard ban imposed in the reformed European Common Fisheries Policy (CFP) enhance the known dilemma of resolving the strain between biological, economic and conservation objectives in fisheries.JRC.G.3-Maritime affair

Questioning the effectiveness of technical measures implemented by the Basque bottom otter trawl fleet: Implications under the EU landing obligation

tThe selective properties of a bottom trawl fitted with a 70 mm diamond mesh codend and a 100 mmtop square mesh panel (SMP) for hake (Merluccius merluccius), pouting (Trisopterus luscus and Trisopterusminutus) and red mullet (Mullus surmuletus) were investigated over the period 2011–2013. The experi-ments were carried out over three separate cruises aboard two commercial Basque bottom otter trawlersin the Bay of Biscay area. “Fall-through” experiments were also undertaken to estimate the potential sizeselection of 100 mm square mesh for the same species. Results from the “Fall-through” experiments andthe at-sea selectivity cruises demonstrated that a 100 mm SMP has the potential to enable undersized andimmature individuals to escape through the meshes. However, the selectivity cruises demonstrated thatin practice, the SMP was largely ineffective at releasing undersized individuals as only a small fraction ofthe fish entering the trawl attempted to escape through the SMP during their drift towards the codend.The fraction attempting to escape was quantified by the “SMP contact probability” and was less than 4%for hake and red mullet and less than 15% for pouting. Furthermore, for each species, the release potentialfor the diamond mesh codend was found to be significantly lower than the length-at-maturity and thelegal minimum conservation reference size. On average, the proportions of the total catch of undersizedindividuals of each species retained by the gear, were 52%, 17% and 45% for hake, pouting and red mulletrespectively. Based on our findings, we conclude that the gear currently deployed by the Basque bottomotter trawl fleet operating in the Bay of Biscay is largely ineffective at releasing undersized hake, poutingand red mullet. The introduction of the obligation to land all catches, under the 2013 reform of the EUCommon Fisheries policy will create new challenges for the Basque bottom otter trawl fleet and therebyan incentive to improve selectivity to avoid unwanted catches of undersized individuals.JRC.G.3-Maritime affair

Model averaging to streamline the stock assessment process

The current fish stock assessment process in Europe can be very resource- and time-intensive. The scientists involved require a very particular set of skills, acquired over their career, drawing from biology, ecology, statistics, mathematical modelling, oceanography, fishery policy, and computing. There is a particular focus on producing a single “best” stock assessment model, but as fishery science advances, there are clear needs to address a range of hypotheses and uncertainties, from large-scale issues such as climate change to specific ones, such as high observation error on young hake. Key to our discussion is the use of the assessment for all frameworks to translate hypotheses into models.Wepropose a change to the current stock assessment procedure, driven by the use of model averaging to address a range of plausible hypotheses, where increased collaboration between the varied disciplines within fishery science will result in more robust advice.JRC.G.3-Maritime affair

What if stock assessment is as simple as a linear model? The a4a Initiative

The current fish stock assessment process in Europe can be very resource- and time-intensive. The scientists involved require a very particular set of skills, acquired over their career, drawing from biology, ecology, statistics, mathematical modelling, oceanography, fishery policy, and computing. There is a particular focus on producing a single “best” stock assessment model, but as fishery science advances, there are clear needs to address a range of hypotheses and uncertainties, from large-scale issues such as climate change to specific ones, such as high observation error on young hake. Key to our discussion is the use of the assessment for all frameworks to translate hypotheses into models. We propose a change to the current stock assessment procedure, driven by the use of model averaging to address a range of plausible hypotheses, where increased collaboration between the varied disciplines within fishery science will result in more robust advice.JRC.G.3-Maritime affair

Testing spatial heterogeneity with stock assessment models

This paper describes a methodology that combines meta-population theory and stock assessment models to gain insights about spatial heterogeneity of the meta-population in an operational time frame. The methodology was tested with stochastic simulations for different degrees of connectivity between sub-populations and applied to two case studies, North Sea cod (\emph{Gadus morua}) and Northeast Atlantic sardine (\emph{Sardina pilchardus}). Considering that the biological components of a population can be partitioned into discrete spatial units, we extended this idea into a property of additivity of sub-population abundances. If the additivity results hold true for putative sub-populations, then the sub-populations are isolated spatial components of the meta-population and assessment results based on sub-populations will provide information to develop and monitor the implementation of finer scale/local management. The simulation study confirmed that when sub-populations are independent and not too heterogeneous with regards to productivity, the sum of stock assessment model estimates of sub-populations' SSB is similar to the SSB estimates of the meta-population. It also showed that a strong diffusion process can be detected and that the stronger the connection between SSB and recruitment, the better the diffusion process will be detected. On the other hand it showed that weak to moderate diffusion processes are not easy to identify and large differences between sub-populations productivities may be confounded with weak diffusion processes. The application to North Sea cod and Atlantic sardine exemplified how much insight can be gained. For the North Sea cod there is a large amount of information that advocates the existence of sub-populations and our results support such claim. In relation to sardine not so much information exists, nevertheless the results obtained were sufficiently robust to support the regional analysis.JRC.D.2-Water and Marine Resource