Data-limited Fisheries Research Articles

Survey-based approach to generate regional multipliers for the Indonesian tropical tuna fisheries

Abstract This study applies surveys of business and household expenditure to draw inferences about the size of regional multipliers to assess the cascading economic impacts of the data-limited Indonesian tropical tuna fishery. The average business-level production multiplier was estimated at around 1.3 across survey respondents, while household-level consumption effects were considerably higher, with the total economic effect roughly three times larger than the production value. A statistical analysis using generalized additive models suggests that there is considerable difference in production multipliers across regions, driven by the individual characteristics of operators, such as revenue/profit, size of the boat, type of gear, and the class of the port where the business is located. This research has the potential to provide a practical management tool to measure flow-on economic impacts of a fishery when information necessary for more formal economic analysis is unavailable, such as for data-limited fisheries or small regional studies.

Assessing the vulnerability of sensitive species in Mediterranean fisheries: insights from productivity-susceptibility analysis

Mortality resulting from interactions with fishing gears represent an important threat to sensitive species globally. In this study, we address this issue by defining five species groups of marine megafauna (marine mammals, seabirds, demersal and pelagic elasmobranchs, and sea turtles), and conducting a productivity-susceptibility analysis (PSA) within the context of data-limited fisheries in the Mediterranean and Black Sea. Although there are significant differences among species within each group, this approach has been considered much more direct and functional for management purposes. The productivity (P) of each species group was determined by evaluating a set of attributes averaged across representative species within each group. Species groups’ susceptibility (S) to bycatch was assessed through a comprehensive review of existing literature and expert judgment, considering a series of semi-quantitative attributes. Our analysis identified areas and fishing gears posing potential risks to the species groups assessed, highlighting that sea turtles and elasmobranchs face the potential risk of incidental captures from various fishing gears operating in both neritic (bottom trawls, set nets and bottom longlines) and pelagic (drifting longlines) environments. Marine mammals exhibit moderate risk across most fishing gears, with particular concern for the harbour porpoise Phocoena phocoena relicta in the Black Sea, primarily due to the interaction with set nets, which can severely impact entire population even capturing few specimens due the species low productivity. Seabirds face reduced impact with fishing activities, irrespective of the type of gear examined or the specific area under investigation. Overall, our study highlights the specific basins and fishing gears requiring focused management measures, mitigation strategies, and enhanced monitoring activities to mitigate the impacts of bycatch on vulnerable marine megafauna.

Biological and fishery indicators for the small-scale marble crab fishery in Northern Patagonia: recommendations for improving a monitoring program and stock assessment of a data-limited fishery

Small-scale fisheries have been typically data-limited despite their economic importance for local communities. This is especially true in zones where fishing operations occur in remote areas under harsh weather conditions. Crab fishery in Chile is exclusively artisanal, and marble crab (Metacarcinus edwardsii) has the highest landing records. This species is found in most parts of the coast of Chile, but it is mainly caught in the south of the country (including Patagonia). Fishery management is data-limited, and monitoring has not established the spatial and temporal variability baseline necessary to determine its exploitation status. This fishery is currently evaluated annually under a scheme based on reporting biological and fishery information, primarily from the landing ports and secondarily from fishing grounds. In the present study, we collected data from fishing grounds on board artisanal fishing vessels around 45°S during an annual cycle to establish indicators based on catch per unit effort (above and below minimum legal size), size, sex ratio, and the relationship between weight and size. Our results showed that fishery and biological indicators respond more to seasonal patterns than to expected spatial heterogeneity related to different fishing grounds: proportional stock density (lowest in winter), sex ratio (biased toward males in winter), retained catch (highest in autumn), and released catch (highest in winter), while the average size of the largest 10% of the sample only showed differences between males and females. Additionally, released catch varied according to soak time, which indicates the effectiveness of escape rings incorporated in the traps. These results lead to recommendations related to the current monitoring program, which should include the selection of a limited number of fishing grounds standardized by season and the incorporation of information related to soak time and the presence of escape rings. Finally, this study highlights the importance of on-board scientific monitoring for any fisheries, even those of small scale.

Fishery-dependent data revealing the spatio-temporal dynamics of under-monitored fisheries

Given that most of the world's fisheries are not properly monitored due to survey programs with limited spatio-temporal coverage, fishery-dependent data provide an opportunity to understand under-monitored species. However, due to the typically poor quality of fishery-dependent data resulting from spatially unbalanced sampling by fishermen, spatio-temporal interactions should be considered during modeling. In this study, we use fishery-dependent catch and effort data collected from fishing log of commercial vessels from 2012 to 2021 to fit a vector autoregressive spatio-temporal (VAST) model to analyze population dynamics of largehead hairtail (Trichiurus lepturus) in the Yellow and Bohai Seas. We considered both fixed and random factors including temporal variations, spatio-temporal interactions, vessel-level variations, and gear types. Our results suggested that the abundance index fluctuated inter-annually and showed a remarkable recovery trend since the large-scale summer moratorium extension in China seas in 2017. Population distributions also showed substantial shifts, with an eastward range expansion especially in the Yellow Sea after 2017. Our study highlights the opportunity of adopting fishery-dependent data to inform the spatial and temporal dynamics of under-monitored fishery species through a proper modeling framework, which may provide a basis for scientific management of data-limited fisheries.

Influence of life history characteristics on data-limited stock status assertions and minimum size limit evaluations using Length-Based Spawning Potential Ratio (LBSPR)

Data-limited fisheries frequently lack age-structure data and instead rely on length-based management and assessment methods. However, the performance of such length-based methods and control rules are often poorly understood when confronted with varying life-history characteristics. In this study, we used Length-Based Spawning Potential Ratio (LBSPR) to conduct a data-limited assessment for a subset of high-value recreational fisheries in California and make inferences about the cumulative performance of existing management regulations. We then simulated stock status under alternative size limit scenarios to estimate the benefit of new or alternative minimum size limits on a species-by-species basis. Here, we present a validated procedure for evaluating minimum size limit scenarios and provide valuable insight on the status of five unassessed fisheries in California, including one species that appears heavily overfished. Furthermore, we identified a range of situations with variable confidence in LBSPR results dependent on life-history characteristics. Most notably, failures in length-based inferences can occur with species that exhibit sporadic recruitment success and spawning aggregation-based fisheries, leading to a hyperstable size structure and potential stock collapse.

Comparison of linear and nonlinear modeling approaches to develop an abundance index based on voyage and market data for a data-limited fishery

IntroductionWorldwide coastal fish resources face severe threats from fisheries overexploitation. However, the evaluation of abundance trends in most coastal fisheries is constrained by limited data. This study took blackmouth croaker (Atrobucca nibe), a stock depleted by coastal trawl fishery in southwestern Taiwan, as an example to showcase the development of a relative abundance index from data-limited fishery (only landing data were available).MethodsThis study employed unique data sourcing from voyage data recorders (VDRs) to estimate fishing effort (in combination with landing data to estimate the catch per unit effort, CPUE) that demonstrated the potential application in global data-limited fisheries and assessed alternative approaches for predictors of fishery-targeting practices to condition effort for producing more accurate metrics of relative abundance. The nominal CPUE was standardized using three statistical models: generalized linear model, generalized additive model (GAM), and vector-autoregressive spatiotemporal models (VASTs) with two treatments of each of the four effects: environmental (sea temperature, salinity, density of mixing layer, seafloor temperature, and chlorophyll), vessel, spatial, and targeting effects. A total of 15 models were designed and compared for these effects, and their explanatory power (EP) was evaluated using cross-validation R2 and other metrics.Results and discussionResults indicated that the targeting effect exerted the most significant influence on standardization and was suggested to be addressed through the principal component analysis (PCA) approach. Both vessel and spatial effects demonstrated considerable influence, whereas the environmental effect exhibited a limited impact, possibly due to the small fishing area in this study. Regarding models’ EP, given the nonlinear nature of the PCA algorithm and environmental data, the study highlighted the superiority of the GAM over linear-based models. However, incorporating nonlinear features in VAST (M15) makes it the most effective model in terms of predictive power in this study. Concerning the stock status, despite variations in relative CPUE trends among major models, a general declining trend since 2015 signals the potential decline of the blackmouth stock and urges fishery managers to consider further design of management measures.

Experiences in developing empirical harvest strategies for the Indonesian tropical tuna fisheries

Harvest strategies, also referred to as management procedures, are foundational to evidence-based fisheries decision making. Together with closed-loop simulation testing, termed Management Strategy Evaluation, of potential harvest strategies, they are considered to be best practice. However, the use of these approaches is still mostly limited to a small minority of high-value, data-rich stocks in developed economies. The Indonesian tropical tuna fisheries provide a rare real-world experience where formal empirical harvest strategies were being developed for data-limited fisheries within a developing economy as an operational management tool. The Harvest Strategy Framework is a departure from a previously open-access fishery for tropical tuna in Indonesian archipelagic waters. It outlines the necessary actions to operationalize the harvest strategy, including fisheries monitoring, harvest control rules, associated management measures to meet the management objectives, and immediate actions to reduce the levels of catch as a precautionary measure until the harvest strategy is fully implemented. It was developed over a 9-year national consultative process, commencing in 2014 and culminating in the official adoption of the framework in June 2023. This paper outlines key processes and challenges encountered in stakeholder engagement and technical capacity development within the intricate governance context of Indonesia. We argue that the engagement processes have cemented a future direction towards sustainable and best practice fisheries management in Indonesia and the effective co-production process has potential to show the way for other fisheries in coastal developing states who face similar challenges in managing their national and internationally shared stocks.

Bridging proxy reference points to sustainable yields to support data-limited fisheries

Many of the world fisheries, especially small-scale fisheries, are in data-limited situations, for which proxy Biological Reference Points (BRPs) derived from per-recruit analyses are widely used to inform fisheries management. However, due to limited information on stock recruitment, per-recruit analyses usually assume constant recruitment and the influences of this key assumption have not been fully understood. In this study, we combined per-recruit analyses and stock-recruit relationship to build equilibrium models for eight species with different life history traits, and used the management strategy evaluation (MSE) framework to assess the uncertainty of proxy BRPs in achieving fisheries sustainability. Our results showed substantial variations in the performances of proxy BRPs on maintaining yield and biomass, and even conservative BRPs, e.g. F0.1 caused overexploitation in half of the cases (4 out of 8). The divergence of the performance between proxy BRPs and FMSY could be substantial, depending on steepness of stock-recruit relationships (correlation ranged from –0.55 to 0.9 for yield, and 0.53 to 0.96 for biomass). Accordingly, we presented an empirical approach for remediation, using correction coefficient to adjust the traditional proxy BRPs. The empirical approach showed satisfactory performances in the validation processes with an independent dataset. This paper demonstrates that proxy BRPs may introduce risks in achieving fisheries sustainability, whereas the errors can be readily adjusted with empirical estimates of steepness for most data-limited fisheries.

Exploitable biomass and acceptable biological catch (ABC) for spiny lobster Panulirus polyphagus from the coast of North Kalimantan, Indonesia using data-limited fisheries

The acceptable biological catch (ABC) can be applied as a management tool to maintain the lobster stock sustainability in North Kalimantan waters where the overfishing condition of lobsters has been detected. Using data-limited fisheries, this study determines the exploitable biomass and ABC of mud spiny lobster (Panulirus polyphagus). The biomass was estimated based on biomass-based length cohort analysis. The exploitable biomass is considered from the biomass at a size larger than the minimum landing size (≥80 mm). The results showed that the total exploitable biomass was estimated as 51,062 kg, and the ABC can be considered as 14,306 kg. The reduction of yields is needed as 26% from the current annual yield to reach the ABC. The catch quota can be given to each fisherman to manage their fishing effort to fill the allowable catch quota. The cooperation between the government, fisherman and market agents is critical to support the implementation of the catch quota system.

A simulation-based option to assess data-limited fisheries off West African waters

Most sophisticated stock assessment models often need a large amount of data to assess fish stocks, yet this data is often lacking for most fisheries worldwide, resulting in the increasing demand for data-limited stock assessment methods. To estimate fish stock status, one class of these data-limited methods uses simply catch time series data and, in other instances, life history information or fishery characteristics. These catch-only methods (COMs) built differently are known to make assumptions about changes in fishing effort and may perform differently under various fishing scenarios. As a case study, this paper used European anchovy (Engraulis encrasicolus) caught in the northwest African waters, though very economically and ecologically important, but still unassessed. Our study investigated the performance of five COMs under different fishing scenarios using as a reference the life-history information of the European anchovy captured in this region of the Atlantic. Hence, the present study developed a simulation approach to evaluate the performance of the five COMs in inferring the stock biomass status (B/BMSY) with consideration of different fishing scenarios under prior information true to anchovy. All five COMs mostly underestimated B/BMSY throughout the simulation period, especially under constant fishing mortality, and in the last five years of the simulation during all fishing scenarios. Overall, these COMs were generally poor classifiers of stock status, however, the state-space COM (SSCOM) generally performed better than the other COMs as it showed possibilities of recovering an overfished stock. When these methods were explored using actual anchovy catch data collected in the northwest African waters, SSCOM yielded results that were deferred from the other COMs. This study being the first to assess this species’ stock in this area using a suite of COMs, presents more insights into the species stock status, and what needs to be considered before scientifically putting in place management measures of the stock in the area.

Syndication of sink-source and area-based resource management as a remedy to sustain a small-scale fishery: The case study of blue swimming crab fishery from Sri Lanka

Tropical small-scale fisheries (SSF) have become more vulnerable to over-exploitation due to: delayed alarming stock status, consequences of implementing deprived management strategies, data-poor scenarios, ambiguous assessment approaches and failures in a comprehensive understanding of the context of specific resource users. Hence, the current study on the blue swimming crab (BSC) fishery off the northern coast of Sri Lanka (September 2017 to November 2018), reveals the evidence of the SSF's requirement for a precise management and decision approach for sustainability. Therefore, here we intended, to evaluate The TropfishR package of the electronic length frequency (ELEFAN) method with new optimization techniques for data-limited fisheries analysis with length frequency (LFQ) data. Further multivariate techniques were used for the follow-up analysis. Results of LFQ data obtained through scrutinized ELEFAN methods and followed-up analysis showed that all studied fishing grounds are overexploited (E > 0.5) due to the “effort-creep” in post-war context and higher economic demand of BSC, which were collectively drive the prevailing behaviour of fishers. Further, due to cultural constraints such as caste-based gear choices and fishing ground choices, the small and immature stages of BSC become more susceptible to gears with low selectivity, which frequently operated in the estuary (ES) and shallow coast (SC). So under this multi-gear, complex SSF scenario banning or restricting the harmful gears becomes socially impossible. Hence, area-based management through a sink-source approach that characterizes the fishing ground with respect to the gear, seems to be promising. Therefore, we conclude that through a such robust approach, we could able to replenish a similarly overfished fishery scenario in the SSF.

Evaluation of Yellow Sea anchovy (Engraulis japonicus) fishery for management strategies using a data-limited management toolkit

Most fisheries in developing countries are data-limited, which creates a huge challenge to the fishery management. Therefore full utilization of the available information is essential. Japanese anchovy (Engraulis japonicus) plays a key role in the marine ecosystem, but the anchovy population in the Yellow Sea of China has declined in the recent decades, which is also a data-limited fishery. In order to implement robust management strategies to recover the anchovy stock, based on the available information as well as the associated uncertainties, here we examine its management strategy evaluation using a computer software package data-limited management toolkit (DLMtool). Results indicated that fishing pressure on the Yellow Sea anchovy should be slightly reduced and the length at first capture should exceed the length at first maturity. These are high probably conductive to anchovy population recovery. We also selected some management procedures performed well in this study, such as minlenLopt1. Paying attention to quantitative population dynamics and perfecting data collection are important for future anchovy fisheries management against uncertainties in both model and data.

Evaluating adaptive management frameworks for data-limited crustacean fisheries

Crustacean fisheries represent an increasingly important contribution to global landings, food security and economic growth, especially in developing countries. However, many productive and valuable crustacean fisheries in Asian countries are characterized by limited data availability, scientific capacity, and fisheries management. Adaptive management frameworks, which use past and emerging information to provide stock status information and management advice, have been touted as particularly applicable for managing capacity- and data-limited fisheries because they employ methods that can improve data collection and result in evaluations of stock and ecosystem status with varying levels of data and capacity. Here, we examined the application of three adaptive fisheries management frameworks (FISHE, FishPath, and DLMtool) to three typical Asian crustacean fisheries that offered contrasting data types and availability, governance, and management and socio-economic contexts. Our aim was to evaluate their suitability for crustacean fisheries and identify particular data and modeling needs and management gaps in these fisheries. We found that while each of the frameworks could effectively recommend suitable monitoring, assessment, and management options given particular contextual factors, there were also limitations with each approach. For example, FISHE took a more wholistic view of ecosystem and fisheries heath, while the other frameworks were more focused on particular aspects of management such as stock assessment (FishPath) and management strategy evaluation (MSE; DLMtool). Applications of each approach also highlighted particular challenges in collecting commercial catch data due to limited monetary investment and poorly designed monitoring programs, which further hindered the implementation of catch and effort limits. The three frameworks also shared common challenges when applied to crustacean species, mainly associated with misalignment with the unique life-histories of crustaceans compared to finfish. By comparing the outputs of the three frameworks, we highlighted their respective strengths and weaknesses and propose an integrated framework that incorporates elements of each of the three frameworks. This integration offers a more comprehensive adaptive roadmap tailored to crustacean fisheries, which involves a mix of qualitative and quantitative approaches that could be applied depending on contextual factors and capacities. To further improve the applicability of adaptive frameworks to crustacean fisheries, we suggest considering crustacean's unique life history and the effects of climate change and other environmental factors, strengthening participatory processes, and balancing socio-economic and ecological objectives.

Effects of data sources and biological criteria on length-at-maturity estimates and spawning periodicity of the commercially important Hawaiian snapper, Etelis coruscans

Reproductive characteristics of a fish stock provide important tools for assessing population health. Change in length-at-maturity (L50) is a potential indicator of exploited fish populations but when criteria for determining maturity classifications are inconsistent, it is difficult to accurately assess change over time and space. Etelis coruscans is a commercially important eteline snapper found throughout the Indo-Pacific, but its region-specific reproductive information in the main Hawaiian Islands (MHI) is sparse. The present study describes length-specific (fork length: FL) female reproductive characteristics of this deep water snapper in the context of a data-limited fishery. We explored the use of six maturity classification criteria based on a functionally mature (containing vitellogenic oocytes and capable of spawning within the season of collection) or physiologically mature (gonadotropin-dependent maturation initiation) designation combined with seasonality and inclusion of additional reproductive phases. Of these classifications, the largest and therefore most conservative estimate was for functional maturity during the spawning period, September-December (L50F = 65.8 cm). Progressively smaller L50 estimates occurred as we incorporated additional reproductive phases and seasonality, the smallest being for physiological maturity during the entire year (L50PY = 50.0 cm). Both functional and physiological maturity criteria are valid for estimating L50 but can yield drastically different parameter estimates based on the definition of mature or immature reproductive phases. Fish that are relatively slow growing, late to mature, and whose fisheries encompass a wide size range, such as E. coruscans, may be more subject to unreliability in the development of their reproductive indicators (length-at-maturity and spawning period) when inconsistent maturity classification criteria are executed over time. We discuss the reproductive characteristics of E. coruscans in the MHI, the use of alternative maturity classification criteria in L50 estimation, the impact on resultant parameters estimates, and the life history implications for the future fishery.

Inferring Stock Status of Painted Spiny Lobster (Panulirus versicolor) in Aru Islands Waters, Indonesia

Three of six commercial spiny lobster species in Indonesian waters was found in Aru Islands waters which exploited continuously using drift gillnet and the catch was dominated by painted spiny lobster (Panulirus versicolor). To ensure the sustainability of the lobster stock, fisheries should be managed properly based on the best available science. In data-limited fisheries, length composition data are most common form information available for researchers and managers since its relatively cheap and simple to collect. In this study, we evaluate the stock status of P. versicolor in Aru Islands waters using three length-based methods: 1) length-converted catch curve (LCCC), 2) length-based spawning potential ratio (LB-SPR) and 3) length-based Bayesian biomass (LBB). The result showed that the mean length at catch of P. versicolor was 80.9 mm in carapace length. Furthermore, the three methods agree that the current status of painted spiny lobster stock seems to be fully exploited where the exploitation rate, the spawning potential ratio, and relative stock size (B/BMSY) were 54%, 35%, and 85%, respectively. Thus, for sustainability of this stock, it is highly recommended to catch P. versicolor at size greater than 80 mm in carapace length.

Diagnosis and Management of Small-Scale and Data-Limited Fisheries

Historically, small-scale fisheries (SSFs) have largely been overlooked by fisheries scientists and management authorities at national and international levels [...]

Evaluation of Biological Reference Points of Two Important Fishery Resources in the East China Sea

Fishery resources play an important role in the national economy and ecological diversity in China; it is of great significance to evaluate and rationally exploit the fishery resources. Most fisheries off the coast of China are data-limited, as the complex assessment models are not suitable for its resource assessment. Therefore, data-limited models for fishery resources assessment in China are among the current research hotspots. In this paper, two new data-limited assessment models (Bayesian state–space implementation of the Schaefer production model (BSM) and Monte Carlo MSY estimation model (CMSY)) were used to evaluate the fishery resources of Scomber japonicus and Muraenesox cinereus in the East China Sea. The results showed that the estimated value of MSY of S. japonicus was 220 × 103 t to 240 × 103 t, the estimated value of F/FMSY was greater than one, and the estimated value of B/BMSY was very close to one, indicating that the fishery in the East China Sea had been overfished. The estimated value of MSY for the M. cinereus fishery in the East China Sea ranged from 140 × 103 t to 170 × 103 t. The estimated value of F/FMSY at the biological reference point was greater than one and the estimated value of B/BMSY was less than one, indicating that the fishery had been overfished and resources had declined. Both models can be used for data-limited fisheries offshore of China. To better understand the impact of uncertainty on fishery resource assessment, more research should be carried out on these two data-limited assessment models.

Resilience of a giant clam subsistence fishery in Kiribati to climate change

Changes in sea surface temperature have historically impacted the coral reef habitats of giant clams in Kiribati. However, across many islands of Kiribati, the four species of giant clam have largely withstood these environmental changes. We adopted and applied a comprehensive resilience framework to assess attributes conferring and limiting resilience in the Kiribati giant clam data-limited fishery and used knowledge co-production and the precautionary principle approach to better understand resilience. We found that the resilience of the fishery to climate and anthropogenic impacts, as highlighted by local stake- and rightholders, will depend on the ability of fishery actors to act collectively to implement adaptive governance. We used a gradient of human pressure to identify approaches and pathways for improving and operationalising climate resilience. Climate change, coupled with human impacts, have reduced ecological resilience in the urbanised island of South Tarawa. In South Tarawa, governance and social processes are less flexible, leading to declines in the local subsistence clam fishery. Conversely, on several remote outer islands, where the social-ecological system has shown promise in combating these anthropogenic influences, the ecological resilience has improved through adaptive community-based fisheries management, and the subsistence clam fishery has persisted. Our case study demonstrates the importance of a participatory approach and local knowledge when assessing climate resilience and identifies a pathway of resilience in a data-limited small-scale fishery. I-KIRIBATI ABSTRACT Ni boong ma taai aika a bwakanako ao bibitakin kabuebuen taari ea bon tia n roota maiun te were nte aro are ea karika te ane ba ena mainaina. E ngae n anne ao utun te were aika a aua (4) aika a kuneaki i Kiribati, a tia n aitara ma kangangan korakoran bibitakin te enwaromenta. Rinanon aia konabwai ni waaki ma bitaki ao a tia naba ni kona ni kaaitarai aia mwakuri ni kabarekareka ao ni karawawata te bota n aomata. Bibitakin kanoan boong, n raonaki ma rikiraken te bota n aomata, ea tia ni kataia ni kauarerekea te konabai ni kaitarai kanganga iaon Tarawa Teinainano ni kabotauaki ma aban Kiribati ake tabeua are e a raroa riki. E korakora te kerikaki ni mwaitin te were iaon Tawara Teinainano ngkai e korakora anaakina ba te amwarake ao ni marau ke ni karako te baronga n aron anaakina. N aban Kiribati ake tabeua ao ea tia ni kakoauaaki ba te baaronga ma te katei n aroaro rinanon kaawan abamakoro ea tia ni kaoka rikiraken ao teimatoan te were bwa te amwarake, e ngae ngke e korakora ana urubwai bibitakin kanoan bong. N taraakin aron bibitakin kanoan boong i Kiribati ma akawan te were, ao e kuneaki ba aron te were ni kona ni kaitara kabuebuen taari ma rikiraken kakangin taari ena boboto man oioi irouia naake a kabongana ke n akawa te were. Te kamatebai aei e riki ba te katoto n aron taneiei ni kaaitarai bitakin kanoan bong n irekereke ma akawa aika a uarereke.

Stock Evaluation of the Data-Limited Fisheries: A Case Study of Five Major Commercially Important Fishes from the Western Indian Ocean, Pakistan

Stock Evaluation of the Data-Limited Fisheries: A Case Study of Five Major Commercially Important Fishes from the Western Indian Ocean, Pakistan

An analytical solution to ecosystem-based FMSY using trophic transfer efficiency of prey consumption to predator biological production.

A theoretical basis for Ecosystem-based Fisheries Management (EBFM) was derived for pelagic fish by applying marine ecology theory of analytical relationships of predator-prey biological production transfers between trophic levels to FAO guidelines for an ecosystem approach to fisheries. The aim is to describe a simple method for data-limited fisheries to estimate ecosystem-based FMSY and how EBFM modellers could mimic the way natural fish communities function for maintaining ecological processes of biological production, biomass and ecosystem stability. Ecosystem stability (ES) FMSY were estimated by proportion of biological production allocated to predators, giving ESFMSY of 0.23 for small pelagic and 0.27 for pelagic finfish, prioritising ecosystem over economics. To maintain both stability and biomass (SB) a full pelagic EBFM SBFMSY of about 0.08 was obtained for both small pelagic and pelagic finfish, having mostly ecosystem considerations. As the FMSY are single-species averages of catchable species targeted in a specific trophic level, multispecies fishing mortalities were proportioned by the biological production of each species in the trophic level. This way catches for each species are consistent with the average ecosystem FMSY for a trophic level. The theoretical estimates gave similar results to other fisheries for sustainable fish catches that maintain the fishery ecosystem processes. They were also tested using six tropical Ecopath Models and showed the effects of imposing commercial fishing mortalities on predominantly EBFM conditions. The ecosystem stability ESFMSY is suggested to be investigated for sustainable fish catches and the full EBFM SBFMSY for protected areas or recovery of heavily depleted stocks.