Fisheries Reference Points Research Articles

Pathways for integrating historical information into fisheries decision‐making

AbstractHistorical information has provided key insights into long‐term ecological change to marine species and ecosystems, with value to fisheries. Yet, pathways to integrate these diverse data sources into fisheries decision‐making have not been clear. Here, we identify an array of biological, ecological, and social information suitable for contemporary science‐based decision‐making, derived from local ecological knowledge, historical archives, archaeological middens and palaeoecological material. We outline two broad pathways to integrate these historical data into fisheries decision‐making, demonstrating that data‐driven use of historical information is relevant across a range of management contexts. First, historical information can inform fisheries assessments that range from simple to complex, affecting indicators of stock status. Second, it can inform estimates of biological potential and social preference, affecting the choice of fisheries reference points. Using the Caribbean Sea as an example, we illustrate these ideas with case studies representing diverse species and historical data types. Integrating historical data can improve indicators of the current state of fish populations and result in management decisions based on a more complete understanding of a potential range of variation, avoiding shifted baselines. The urgency of this work is underscored by accelerating environmental changes and the rapid loss of invaluable historical information sources. By illuminating pathways, our goal is to increase the accessibility of these types of information and to underscore that scientists, managers, and resource users have roles to play in identifying and integrating relevant long‐term data at various spatial and temporal scales to sustainably manage marine fisheries.

White sardine (Escualosa thoracata) stock status in coastal waters of Bangladesh

AbstractThe marine fisheries of Bangladesh have experienced an uncontrolled expansion of fishing over the last few decades. Consequently, most fish stocks became vulnerable to overfishing. Similar to many other fisheries, catch of white sardine (Escualosa thoracata) is rapidly declining. Therefore, three data‐limited approaches (length‐based Bayesian biomass analysis, LBB; length‐based spawning potential ratio, LB‐SPR; and Froese's length‐based indicators, LBIs) were used to estimate growth, mortality, and fisheries reference points to evaluate stock status of the white sardine fishery. Results revealed that the fishery is being overfished: F/M = 1.32 years−1 in LBB and 6.67 years−1 in LB‐SPR. However, the stock biomass is still good with B/B0 = 0.43 and B/BMSY = 1.20. Stock indicators revealed that the fishery was mainly targeting mature fishes, most of which were mega‐spawners (older, larger fish), which suggested stocks were recruitment overfished. Harvesting an optimum size range (6.57 to 8.03 cm) and reducing fishing mortality to a sustainable level (F = M) would sustain a healthy stock biomass.

Estimation of Atlantic bonito (Sarda sarda) stock status in the Senegalese Exclusive Economic Zone (SEEZ) from the catch-based model (CMSY) and length-based bayesian estimation (LBB) method

Among the seven major small tuna species defined in the ICCAT priority list for future studies, Atlantic bonito (Sarda sarda) is the most heavily targeted by artisanal and industrial fisheries in many coastal areas. Considering this high pressure and the limits of previous studies on its status in some areas of the Atlantic Ocean, this study focused on assessing the Atlantic bonito stock mainly harvested by the artisanal fisheries in the Senegalese Exclusive Economic Zone (SEEZ) using two data-limited approaches (LBB and CMSY). These models used the recorded length composition, catch, and CPUE data for Atlantic bonito caught by various fishing gears to provide significant fisheries reference points to evaluate the stock status of this species. The LBB model indicated an Atlantic bonito healthy stock status with B/BMSY values ranging from 1.3 to 1.6 and B/B0 values varying from 0.47 to 0.61 of the main scenarios performed (BON_AFG_CL, BON_GN_Length, and BON_PS_Length). The results estimated by LBB are consistent with those obtained by CMSY. The CMSY model results demonstrate that the SEEZ Atlantic bonito stock is in a sound condition in the final year of the main scenarios analyzed (BON, BON-bt, BON-GN-bt, and BON-PS-bt) with sustainable relative stock biomass (B2018/BMSY= 1.13 to 1.3) and fishing pressure levels (F2018/FMSY= 0.52 to 1.43). However, the results of the two models show that longlines and sleeping nets negatively affect this species’ stock in this area, showing a slightly overfished and overfished stock status, respectively. The results of the scenarios formulated by these two fishing gears (BON_LL_Length, BON_SN_Length for LBB and BON-LL-bt, BON-SN-bt for CMSY) are below the reference values. LBB shows Lc/Lc_opt values ranging from 0.61 to 1, B/BMSY from 0.49 to 1, and B/B0 from 0.18 to 0.39. For CMSY, these two scenarios show a B/BMSY varying between 0.33 and 0.8.

Clupeids in the kaptai reservoir, a blessing or a curse: estimation of fisheries reference points

Sustainable fisheries management depends on the degree of the present exploitation status of significant fish stocks. A recently developed fish stock assessment approach, CMSY, was used to estimate the fisheries reference points of data-limited Gudusia chapra and Corica soborna from the Kaptai reservoir using catch data, resilience, and exploitation records during the first and last year of the time series catch data. CMSY, along with a Bayesian state-space Schaefer production model (BSM), estimated maximum sustainable yield (MSY) as 2680 mt and 2810 mt, and 3280 mt and 3020 mt for the above stocks, respectively. The MSY range for both stocks was higher than the last catches meaning that both stocks are perfectly sustainable. The lower biomass B (4340 mt) for G. chapra estimated by CMSY and BMSY (4490 mt) indicates that the stock has started to be depleted. However, considering the precautionary fisheries management, the lower limit of MSY might be suggested to follow. Therefore, it could be suggested not to exceed the MSY limit (2680 mt) for the sustainability of G. chapra stock while it was 3020 mt for the C. soborna fishery. The intrinsic growth rate r was 0.862–1.19 yr−1 for G. chapra and 0.428–0.566 yr−1 for C. soborna, suggesting a high and medium increase of biomass in the existing population, respectively. A F/FMSY less than 1 and B/BMSY greater than 1 report both stocks at underfishing and underfished states. The study recommends enforcing strict and lawful actions regarding the net's mesh size to catch less small fish. Otherwise, negligence of this crucial management practice may bring severe threats to the sustainability of the whole reservoir resources and the reservoir ecosystem.

Stock Assessment of Red Mullet, Mullus barbatus Linnaeus, 1758 by Length-based and Catch-based Models in the Northeastern Mediterranean

Stock assessment for Mullus barbatus using catch-based (CMSY) and length based (LBB, LBSPR and LIME) data limited models were performed by using official catch statistics and commercial length frequency data from northeastern Mediterranean. The CMSY model results showed that the catch amount did not exceed MSY, and the fisheries reference points (B/BMSY and F/FMSY) indicated a healthy stock status in 2020. The LBB model results indicated that the biomass ratio was above safe biological limits (B<0.5 BMSY) but fishing mortality was slightly higher than natural mortality. Likewise, LBSPR results showed that SL50 for red mullet was higher than its Lm50, while the estimated median SPR was above the limit of 20% set as the biological reference point. The LIME results were more optimistic than those from the LBB and LBSPR and the estimated SPR was found above 40% which is the target reference point for a sustainable stock. According to the results of different assessment models, the red mullet stock was deemed sustainable in terms of biomass but observation of fishing pressure is required.

Optimum capture size of Trichiurus japonicus in the East China Sea.

Trichiurus japonicus is an economically valuable species in the East China Sea, whose allowable capture size varies with fishing effort in different years. To clarify the optimum capture size for T. japonicus in the East China Sea, we collected samples and data from T. japonicus targeting fishing gears such as trawls, canvas spreader stow nets and longlines from 2016 to 2020. We estimated growth and mortality parameters using the FiSAT II software, and calculated the size limit standards for capture. The results showed that the inflection point of anal length, the critical anal length and the anal length of one-year-old T. japonicus was 382.84, 397.12, and 216.05 mm, respectively. The anal length of maturity was 230.38 mm, and the minimum capture size (anal length) was 219.23 mm. Based on the yield per recruitment analysis using Beverton-Holt model, the current fishery reference points were under overfishing condition (tc=0.38 a, F=2.11), and the suggested optimum capture size was 364.64 mm. There would be a sharp decline of T. japonicus catches in the East China Sea if the suggested minimum capture size was substantially higher, which might be non-practical for local fishermen. Therefore, we suggested 220 mm as the capture size limit, which was close to the anal length of one-year-old fish and the anal length of maturity.

Barriers to implementation of dynamic reference points in fisheries management

Fish populations are dynamic; their productivity depends on the environment, predator and prey interactions, and fisheries harvest rates. Failure to account for these factors in fisheries science and management can lead to a misestimation of stock dynamics and productivity, resulting in overexploitation or forgone fisheries yield. Using an online survey, we asked fisheries scientists, industry stakeholders, Indigenous partners, and non-governmental organizations whether changing ecosystem productivity was a problem in their experience, how often dynamic approaches to fisheries reference points have been adopted, what methods had been used, and what fisheries they had been applied to. Changing fisheries or ecosystem productivity was reported as an issue by 96% of respondents; however, 74% of respondents said they had never seen dynamic reference points implemented, 16% said in very few instances, while 10% said frequently. The most common barriers to implementation of dynamic approaches in fisheries management were institutional inertia and uncertainty about whether a change in productivity was lasting. We discuss trade-offs between fisheries management performance and stability.

Fisheries Reference Points under Varying Stock Productivity and Discounting: European Anchovy as a Case Study

European anchovy (Engraulis encrasicolus) is the main commercially exploited fish stock in the Black Sea region, providing a vital source of livelihood and revenue for local communities and national economies. In recent decades, the Black Sea anchovy stock has faced many human-induced threats, including overfishing, eutrophication, invasive species, and climate change while these threats have raised concerns about the status and long-term productivity of the stock. To ensure sustainable levels of exploitation under potential future changes in stock productivity, we here estimate and compare a suite of biological and economic reference points under different levels of stock productivity and discount rates using an age-structured bioeconomic model setup. Our model simulations showed that optimal fishing mortalities achieving maximum sustainable yield (FMSY) and maximum economic yield (FMEY) increase at higher stock productivity but are always lower than the historically high mean levels of exploitation. Furthermore, we illustrate that the stock biomass at maximum economic yield (BMEY) is larger than the stock biomass at maximum sustainable yield (BMSY) at all stock productivities and discount rates, except at low stock productivity under high levels of discounting (i.e., 10%, 20%). By illustrating the ecological and economic benefits of reducing exploitation rates, we expect that our estimated reference points can add value to the decision-making process for the management of the European anchovy fishery and ensure long-term sustainable management even under future climate-driven changes in stock productivity.

Shifting baselines and deciding on the desirable form of multispecies maximum sustainable yield

AbstractMultispecies, multigear fisheries occur in most ecosystems in the world, but are typical in tropical ecosystems and especially in emerging economies. However, much of fishery science has been developed from a single-species perspective. Management schemes based on single-species reference points often ignore the trophic link among species and the technical interaction between gears, essentially disconnecting management objectives from the context of an ecosystem—or socioecological system—where fisheries operate. Using the Gulf of Thailand fishery as an example, we demonstrate how aggregate production models can be used to estimate system-level fishery reference points for multispecies fisheries. Our results show that the multispecies maximum sustainable yield changes with ecosystem state—the systemic productivity level due to species composition and ecological (trophic/habitat, etc.) structure—under various development levels of fishing and varies with management objectives such as biodiversity, system resilience, total catch, total value, and employment. Aggregate approaches are a tractable way of estimating sustainable ecosystem-scale extraction for multispecies fisheries, avoiding the dilemma of facing conflicting advice derived from single-species methods and providing a practical, operational step toward ecosystem-based management. However, these methods are sensitive to the ecosystem states over time and decision makers need to make informed decisions on which state they want to maintain (or recover) and thus which system-level reference points to use. Consequently, management of multispecies fisheries must be clear on their system-level fisheries policy objectives.

Assessing the Distribution and Sustainable Exploitation of Lophius litulon in Marine Areas Off Shandong, China

In recent years, the proportion and economic value of Lophius litulon (family Lophiidae) in the coastal fishery off Shandong Province, China has increased. In this study, we mapped the distribution of L. litulon abundance [catch per unit effort (CPUE)] and applied a generalized additive model (GAM) to explore the relationship between CPUE and environmental factors. Two data-limited methods (the BSM related to the CMSY method and the AMSY method) were used to evaluate the stock status and relevant fishery reference points of L. litulon. The results showed that the L. litulon stock was concentrated in the central Yellow Sea, at 34.0°–37.0° N and 121.0°–124.0° E, and the highest average CPUE of L. litulon in this area occurred in winter. The three most significant environmental factors affecting species abundance were bottom temperature, bottom salinity, and depth. L. litulon was most abundant when bottom temperature ranged from 5.8 to 10.6°C, depth was > 18 m, and bottom salinity varied from 31.0 to 33.2‰. The BSM and AMSY models indicated that the L. litulon stock was unhealthy and had been overfished in recent years, as its biomass remained below the level that can support maximum sustainable yield. The relative exploitation ratios were also high. These results provide the basic data for improving sustainability of the exploitation of L. litulon in the Yellow and Bohai Seas.

Fisheries Reference Point and Stock Status of Croaker Fishery (Sciaenidae) Exploited from the Bay of Bengal, Bangladesh

This research evaluated fisheries reference points and stock status to assess the sustainability of the croaker fishery (Sciaenidae) from the Bay of Bengal (BoB), Bangladesh. Sixteen years (2001–2016) of catch-effort data were analyzed using two surplus production models (Schaefer and Fox), the Monte Carlo method (CMSY) and the Bayesian state-space Schaefer surplus production model (BSM) method. This research applies a Stock–Production Model Incorporating Covariates (ASPIC) software package to run the Schaefer and Fox model. The maximum sustainable yield (MSY) produced by all models ranged from 33,900 to 35,900 metric tons (mt), which is very close to last year’s catch (33,768 mt in 2016). The estimated B > BMSY and F < FMSY indicated the safe biomass and fishing status. The calculated F/FMSY was 0.89, 0.87, and 0.81, and B/BMSY was 1.05, 1.07, and 1.14 for Fox, Schaefer, and BSM, respectively, indicating the fully exploited status of croaker stock in the BoB, Bangladesh. The representation of the Kobe phase plot suggested that the exploitation of croaker stock started from the yellow (unsustainable) quadrant in 2001 and gradually moved to the green (sustainable) quadrant in 2016 because of the reduction in fishing efforts and safe fishing pressure after 2012. Thus, this research suggests that the current fishing pressure needs to be maintained so that the yearly catch does not exceed the MSY limit of croaker. Additionally, specific management measures should implement to guarantee croaker and other fisheries from the BoB.

Using the LBB Method for the Assessments of Seven Fish Stocks From the Yangtze Estuary and Its Adjacent Waters

The status of fishery resources in the Yangtze estuary and its adjacent waters is still unclear for the effective implementation of fishery management strategies. To help address this gap, a new method especially for data-limited fish stocks (LBB) was applied to assess seven commercially and ecotrophically important fish stocks. Fish specimens were collected in the estuary by bottom trawling quarterly from May 2018 to February 2019. Two historical datasets were collected with the same method in the same area for Indian perch (Jaydia lineata) and sickle pomfret (Pampus echinogaster). To explore the growth features and resilience of fish stocks, auximetric plots and growth performance indices (Φ′) were used. Results showed that common hairfin anchovy (Setipinna tenuifilis) in 2018 and Indian perch in 2018 showed a healthy stock biomass status with complete length structures under a sustainable fishing pressure. The others were outside of safe biological limits or overfished. The Lmean/Lopt < 0.9 in six (67%) of nine LBB models for seven fish stocks suggested that most of the stocks were truncated in length structures. This contribution provides the main fishery reference points regarding stock status that can inform managers and form the basis for various management strategies.

Fish Stock Assessment for Data-Poor Fisheries, with a Case Study of Tropical Hilsa Shad (Tenualosa ilisha) in the Water of Bangladesh

The anadromous tropical Hilsa shad formed the largest single-species fishery in Bangladesh, making the highest contribution to the country’s total fish production (14%) and nearly 83% of the global Hilsa catch in 2018. However, increased fishing pressure made the fishery vulnerable, and hence, information on the stock condition and its response to the current degree of removal is essential to explore the future potential for sustainable exploitation. This study carried out a rigorous assessment based on three different methodological approaches (traditional length-frequency based stock assessment method for fishing mortality and exploitation, Froese’s length-based indicators for fishing sustainability, and a surplus production-based Monte Carlo method-CMSY, for fisheries reference points estimation) for the best possible estimates of the Hilsa stock status in the water of Bangladesh. The present findings revealed that the stock is likely to be overfished due to over-exploitation. Depending on the outputs, this study recommended a lower length limit for the catch (>33 cm), distinguished a selectivity pattern (mesh size limit ≥ 8 cm), and proposed a yearly landing limit (within the range of 263,000–315,000 tons) for the sustainable management of the Hilsa fishery in Bangladesh.

Assessment of 11 Exploited Fish and Invertebrate Populations in the Japan Sea Using the CMSY and BSM Methods

The catch-maximum sustainable yield (CMSY) method and a closely-related Bayesian state-space Schaefer surplus production model (BSM) were combined with published catch-per-unit-effort (CPUE) time series or spawning stock biomass (SSB) data to evaluate fisheries reference points for exploited resources of the Japan Sea. Eleven fish and invertebrate stocks were assessed; outcomes obtained through this analysis were the carrying capacity, biomass trajectory, maximum sustainable yield, and related parameters of each stock. Results showed that the stock of Japanese sandfish (Arctoscopus japonicus) was slightly overfished; the stocks of sohachi (Cleisthenes pinetorum), flathead flounder (Hippoglossoides dubius), bastard halibut (Paralichthys olivaceus) and snow crab (Chionoecetes opilio) were overfished; and the stocks of shotted halibut (Eopsetta grigorjewi), yellow striped flounder (Pseudopleuronectes herzensteini), red seabream (Pagrus major), Alaska pollock (Gadus chalcogrammus) and deep-sea smelt (Glossanodon semifasciatus) were grossly overfished; only Alaskan pink shrimp (Pandalus eous) was in a good condition. These results are consistent with the few previous studies on the status of fish species around Japan, where overfishing is becoming increasingly apparent. These assessments provide a basis for guiding the use of fishery resources in the Japan Sea.

Towards the rebuilding of spiny lobster stocks in Brazil: a review

Abstract In this study, we used the Monte Carlo model (CMSY) to estimate fisheries reference points based on annual lobster landings. During the period 2012-2018, fishing pressure on lobster stocks decreased and a tendency for recovery was observed, despite the low biomass levels of approximately 29%. In 2019, the stock size was capable of producing yields close to the maximum sustainable yield (5770 t), with a probability of 58.1%. The enforcement of management measures should be continued in order to eliminate sources of negative externalities and rebuild stocks. We also demonstrate that the closed season does in fact protect the main events of the lobster life cycle. Responsible and efficient management should focus on life cycle studies and reliable monitoring of fishing data.

Evaluating Stock Status of 16 Commercial Fish Species in the Coastal and Offshore Waters of Taiwan Using the CMSY and BSM Methods

The waters around Taiwan are impacted by the Kuroshio and coastal currents, resulting in a high productivity and a high diversity of marine life. As a consequence, there are a multitude of fisheries around Taiwan, conducted by a fleet that has grown enormously in the last four decades. Here, we investigate the effect of the resulting fishing pressure on sixteen commercial fish stocks including demersal and pelagic species in the coastal and offshore waters of Taiwan using the CMSY and BSM methods. Both of these methods required principally catch time series, with the BSM methods also requiring CPUE data. The results show that of the 16 assessed stocks, 10 stocks have collapsed, 2 are severely overfished, 2 are overfished, 1 is slightly overfished and only 1 stock remains in a healthy status; these troubling results are attributed to excessive fishing pressure. However, climate-driven environmental variability may be another factor affecting the fishery resources around Taiwan, as evidenced by chub mackerel Scomber japonicus, the one stock deemed healthy, which is here attributed to favorable environmental condition. Using the fisheries reference points provided here, rebuilding plans could be provided for the other 15 species; however, such plans are not likely to be successful without reducing the size of the Taiwanese fishing fleet.

Fisheries for the future: greenhouse gas emission consequences of different fishery reference points

Abstract Global fisheries have for long been scrutinized in terms of ecosystem effects but only more recently for their greenhouse gas emissions. These emissions are dominated by fuel use on fishing vessels and the levels are often neglected side effects of resource overexploitation. Using a simple production model, Pella-Tomlinson, we illustrate how fuel efficiency (fuel use per unit of catch) varies with the level of exploitation and biomass depletion. For this model, fuel use per unit catch rises hyperbolically with fishing effort—it is relatively flat at low levels of effort but rises steeply as effort increases and biomass and catch decline. In light of these findings, the general fuel efficiency relationship with common fishery reference points on stock status is discussed, as well as other means of reducing fuel use and thus greenhouse gas emissions. We conclude that much may be gained by considering fuel efficiency in setting reference points for target stock biomass in fisheries and encourage further investigations.

Stock dynamics of the brushtooth lizardfishSaurida undosquamis(Richardson, 1848) from a tropical multispecies fishery in the southeastern Arabian Sea

The brushtooth lizardfishSaurida undosquamis(Richardson, 1848) is a high trophic level benthic predator and is one among the most exploited demersal finfish species from eastern Arabian Sea by Indian trawlers. However, in recent years, the landings of many top predator fishes includingS. undosquamisshowed a declining trend resulting in a steady decline in the mean trophic levels of the fishes caught commercially in the region. We investigated the growth, mortality and stock dynamics ofS. undosquamisharvested by mechanised trawls in the southeastern Arabian Sea, using length-based methods for the data collected during 2012–2016. Besides, Bayesian state-space implementation of the Schaefer model (BSM) and catch-based MSY (CMSY) estimation were also made using the data for the period 1985–2016. Total length of the fish ranged from 5.5 to 34.5 cm with average annual mean length of 22.0 cm during 2012–2016. The growth parametersL∞andKwere 37.3 cm and 0.41 year−1, respectively. The natural, fishing and total mortality coefficients were 0.92, 2.58 and 3.5, respectively and exploitation ratio was 0.82. The length at first maturity was estimated at 21.4 cm for females. The mean size in the catch is lower than the optimum length for exploitation. Fisheries reference points (MSY, Fmsy, Bmsy) as well as relative stock size (B/Bmsy) and exploitation (F/Fmsy) estimated from catch data and broad priors for resilience (r), implies an exploitation of 30% below Bmsylevel. Results from the length-based Thompson and Bell prediction model indicates that reducing the present level of fishing effort by 40% would lead to a harvest of the species at a sustainable level. As “fishing down food web” is reported in recent years from eastern Arabian Sea, the exploitation of top predators need to be maintained at sustainable levels to prevent ecosystem changes along the region.

Spatial variability in the growth of Sheepshead (Archosargus probatocephalus) in the Southeast US: Implications for assessment and management

Understanding geographic variation in growth dynamics is essential for the management of exploited fish populations because such variation can be used to define stock structure and influence perceptions of stock productivity. Sheepshead (Archosargus probatocephalus) is a species targeted by both commercial and recreational fisheries, and is distributed throughout the north and central Atlantic Ocean and Gulf of Mexico. We analyzed fishery-dependent and –independent length-at-age and weight-at-length data from Texas, Louisiana, Mississippi, Alabama, Florida, South Carolina, North Carolina, and Virginia to investigate the geographic variation in growth of Sheepshead. We constructed a series of von Bertalanffy growth functions (VBGF) and length-weight power equations using a Bayesian framework that included sex, latitudinal, and regional effects. Median posterior VBGF parameter estimates of asymptotic length (L∞) for females ranged from 561 mm fork length in the Virginia Chesapeake Bay to 418 mm in Florida Gulf coast, while the posterior median growth coefficient (k) ranged from 0.42 yr−1 in Texas to 0.20 yr−1 in the Florida Atlantic. Predicted length-at-age and weight-at-length varied considerably among States. Predicted length-at-age for age-1 and -5 individuals was greater in the Gulf of Mexico than the Atlantic. However, predicted length-at-age for older age classes was greater in the Atlantic. Predicted weight-at-length decreased along latitudinal gradients in the Atlantic and the lowest values were found in Mississippi. Given the impact of growth on fisheries reference points, such geographic variation in growth can inform the development of assessment efforts for Sheepshead in the Gulf of Mexico and Atlantic.

Shifts in North Sea forage fish productivity and potential fisheries yield

Abstract Forage fish populations support large scale fisheries and are key components of marine ecosystems across the world, linking secondary production to higher trophic levels. While climate‐induced changes in the North Sea zooplankton community are described and documented in literature, the associated bottom‐up effects and consequences for fisheries remain largely unidentified. We investigated the temporal development in forage fish productivity and the associated influence on fisheries yield of herring, sprat, Norway pout and sandeel in the North Sea. Using principal component analysis, we analysed 40 years of recruitment success and growth proxies to reveal changes in productivity and patterns of synchroneity across stocks (i.e. functional complementarity). The relationship between forage fish production and Calanus finmarchicus (an indicator of climate change) was also analysed. We used a population model to demonstrate how observed shifts in productivity affected total forage fish biomass and fisheries yield. The productivity of North Sea forage fish changed around 1993 from a higher average productivity to lower average productivity. During the higher productivity period, stocks displayed a covariance structure indicative of functional complementarity. Calanus finmarchicus was positively correlated to forage fish recruitment, however, for growth, the direction of the response differed between species and time periods. Maximum sustainable yield (MSY) and the associated fishing mortality (Fmsy) decreased by 33%–68% and 26%–64%, respectively, between the higher and lower productivity periods. Synthesis and applications. The results demonstrate that fisheries reference points for short‐lived planktivorous species are highly dynamic and respond rapidly to changes in system productivity. Furthermore, from an ecosystem‐based fisheries management perspective, a link between functional complementarity and productivity, indicates that ecosystem resilience may decline with productivity. Based on this, we advise that system productivity, perhaps monitored as forage fish growth, becomes an integral part of management reference points; in both single species and ecosystem contexts. However, to retain social license of biological advice when fish catch opportunities are reduced, it is crucial that shifts in productivity are thoroughly documented and made apparent to managers and stakeholders.