Stock Status Research Articles

Environmental drivers affecting the status of top commercial fish stocks in the Baltic Sea: review

IntroductionLike in many parts of the world, the Baltic Sea experiences a multitude of processes and stressors that influence fish stock dynamics. This paper compartmentalizes 250 publications that examine the cumulative effects and trade-offs of some of the most significant environmental drivers (temperature change, hypoxia, nutrient enrichment, acidification, low salinity, and food-web dynamics) on the ecology of top commercial fish species in the Baltic Sea (cod, sprat, whiting, herring, flounder, and plaice).MethodsA systematic review method was applied to ensure rigorous coverage of existing literature and to provide a comprehensive synthesis of the current knowledge on the subject.ResultsThe results illustrate the extent of scientific research applicable to commercial fisheries knowledge in the Baltic Sea and identify which pressures have the greatest negative impacts on which stocks. Additionally, the findings demonstrate how well top commercial fish species have adapted to the changing environmental conditions of the Baltic Sea. In doing so, the review illustrates the upcoming challenges and underscores which stocks are likely to dominate in the future and which will face difficulties.DiscussionBy considering ecosystem-based fisheries management, this paper emphasizes the need to account for complex ecosystem interactions beyond single-stock monitoring. With increased natural hazards, top commercial fish species have reacted differently, depending on the region and their adaptive capabilities. In most cases, Clupeidae species have adapted the best to their new surroundings, Pleuronectidae resilience is varied, while Gadidae species are finding the Baltic Sea increasingly challenging.

Analysis of blue swimming crab (Portunus pelagicus) stock in Banten Bay waters based on spawning potential ratio methods

Abstract Blue Swimming Crab (BSC) (Portunus pelagicus) is the main commodity in Banten Bay with fishing activity throughout the year. The increasing fishing pressure has led to a decrease in the average size of the BSC carapace width. This situation is indicative of overfishing of BSC and it can have negative effects on the stock of BSC. This study aimed to determine the stock and condition status of BSC based on the results of research conducted from December 2021 to February 2022 in the waters around Banten Bay. Data were collected using direct observation and simple random sampling from fishers at each landing site with a total sample of 7244 consisting of 4448 males and 2796 females. Data analysis using the Fisat II and web-based application http://barefootecologist.com.au/. The results showed that the stock status of BSC in Banten Bay resulted in an SPR value of 21% or below the sustainability target. The catch of BSC males was more than females with a ratio of 1.59:1. The length at first capture (Lc) females was 117.3 mm and the length at first mature/adult (Lm) was 103 mm. The length at first capture size was greater than the length at first mature which showed catch-worthy.

Life History Parameters and Spawning Potential Ratio of Upeneus vittatus (Forsskål, 1775) in the Coastal Waters of Lebak and Sukabumi, Indonesia

Abstract It is necessary to obtain information regarding the life history and stock status of the yellow-striped goatfish (Upeneus vittatus) in the coastal waters of Lebak and Sukabumi, Indonesia. This study aims to determine the stock status of U. vittatus in the coastal waters of Lebak and Sukabumi based on their life history parameters and length-based spawning potential ratio (LB-SPR). Eight hundred seventy-four samples were collected from Binuangeun, Palabuhanratu Nusantara, and Ciwaru Fishing Ports. The monthly length frequency data were obtained from July to December 2022. The results show that the Von Bertalanffy growth parameter was Lt=254(1-e−(0.58(t+0.154)) for males, Lt=239(1-e−(0.42(t+0.221)) for females, and Lt = 258(1-e−(0.37(t+0.246)) for both. The mature gonads of U. vittatus were mostly obtained from October to December. The length of first maturity L50 and L95 were 158 mm and 236 mm for males and 149 mm and 229 mm for females, respectively. The exploitation rate (E) on male, female, and combined U. vittatus revealed that E values exceed 0.5 or are overexploitation. The estimated SPR of U. vittatus was 23%, lower than the target reference point of 40%. Therefore, U. vittatus was fully exploited in the coastal waters of Lebak and Sukabumi.

Religious Investor Sentiment, Shariah Compliance Impact, and Theological Risk: Evidence from Bursa Malaysia

This study examines the financial implications of religious restrictions by analyzing how changes in the Shariah compliance status of stocks affect their price and trading volume. Employing the market model in an event study approach and using data from Malaysian firms between 2000 and 2016, the study focuses on 30 announcements from the Security Commission Malaysia’s List of Shariah Compliant Securities (LSCS), resulting in 370 additions and 284 deletions from the compliance list. The findings indicate that the inclusion of stocks in the compliance list generates longterm demand driven by Islamic institutional and Muslim retail investors, leading to a permanent increase in abnormal returns and trading volume. Conversely, the removal of stocks from the compliance list induces short-term negative abnormal returns and increased trading volume, reflecting selling pressure. These results contribute to understanding the financial consequences of religious restrictions, highlighting the influence of Shariah compliance on stock market performance and investor behaviour.

Assessments of 12 Commercial Species Stocks in a Subtropical Upwelling Ecosystem Using the CMSY and BSM Methods

Twelve commercial species exploited in the eastern Guangdong and southern Fujian waters were assessed using the Catch-Maximum Sustainable Yield (CMSY) and Bayesian Schaefer Model (BSM) methods. The carrying capacity (k), intrinsic rate of population growth (r), maximum sustainable yield (MSY), and relative biomass (Bend/k and B/BMSY) were estimated. The current stock status was defined by B/BMSY and fishing mortality (F/FMSY). The results indicate that seven stocks were overfished or below safe biological limits (B/BMSY < 0.5 or F/FMSY > 1), two stocks were in a recovery phase (0.5 < B/BMSY < 1, F/FMSY < 1), and three stocks were under sustainable fishing pressure with healthy biomass, capable of producing yields close to the MSY (B/BMSY > 1, F/FMSY < 1). The stock statuses are consistent with previous studies on the utilization of pelagic fisheries in the eastern Guangdong and southern Fujian waters and with those assessments in other waters. The results of the assessments suggest that these stocks could be expected to produce higher sustainable catches if permitted to rebuild; thus, more effective and proactive management is needed in this upwelling fishing ground.

Towards sustainable exploitation of European pilchard (Sardina pilchardus) stocks off West African waters

European pilchard (Sardina pilchardus), herein referred to as “sardine” or “European sardine”, is the most productive and economically important small pelagic fish in the Northwest African waters. Thus far, very little is known about its stock status in the West African region despite the rapid decadal increase in its catch production. The present study provides avenues vital to improving guidance for sustainable species management. In this region, sardine is divided administratively into three stocks (northern: stock N, central: stock A + B, and southern: stock C). Thus, the present study used two Surplus Production Models (SPM) to evaluate sardine's stock status. Sardine's catch and scientific survey biomass data obtained from FAO-CECAF's (Fishery Committee for the Eastern Central Atlantic (CECAF)) latest reports were used in this analysis to fit the SPMs and investigate the effectiveness of the available catch-per-unit-effort (CPUE) trends in setting the total allowable catch (TAC) for sustaining the different sardine stocks in the region. Results from the SPMs indicate that the sardine stock in the north is fished at optimum levels. Meanwhile, the SPMs output based on the scientific survey biomass indices indicated a healthy state for the central and southern sardine stocks. Similarly, the fishery CPUE indices for the central and southern stocks showed similar biomass trends compared to the survey biomass index, indicating healthy stock status. Therefore, in cases where survey biomass index data is unavailable to run stock assessments, this study suggests that sardine fishery CPUEs could be used in SPMs to monitor biomass trends over time and may also provide stock status proxies. Additionally, with rapid climate and other environmental changes, sardine stocks must be regularly monitored with consistent and comparable scientific methodologies and updated fisheries time series data.

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.

Evaluating stock status of shortfin mako (Isurus oxyrinchus) in southern Java and West Nusa Tenggara, Indonesia, using length-based approach

Evaluating stock status of shortfin mako (Isurus oxyrinchus) in southern Java and West Nusa Tenggara, Indonesia, using length-based approach

Genetic diversity and population structure of Pacific abalone (Haliotis discus hannai) using SNP genotyping data

The Pacific abalone Haliotis discus hannai is one of the most valuable mollusks in China. It also supports an important fishery in the northern coast of China, which has shown a declining tendency. The conservation of this species is attracting attentions under the potential threats of alien stocks and hybrid varieties disseminated in aquaculture. However, population genetics information on whole-genome level is lacking. The present study analyzed the genetic diversity, population structure, and inbreeding coefficient of nine populations collected from China and Japan using single nucleotide polymorphism (SNP) genotyping data from 214 samples. The results showed higher observed heterozygosity (Ho) than expected heterozygosity (He), and negative inbreeding coefficient (Fis) values indicating an excess of heterozygotes, and highlighting medium to high genetic diversity within the population. The genetic structures of the nine populations were categorized into three distinct subgroups. Pairwise Fst values based on all SNP loci and those for neutral markers were consistently low, indicating an overall genetic homogeneity between the populations. The distribution of runs of homozygosity (ROH) lengths suggests the potential occurrence of kinship relationships in various historical periods, including both distant and recent periods. The TreeMix and shared haplotypes suggested strong gene flow from Japanese populations of Pacific abalone to Chinese populations. These findings establish the stock status of the Pacific abalone in China, providing a basis for conservation, fishery management and utilization of the stocks in aquaculture.

Distribution and abundance of ichthyoplankton in natural al artificial reefs in Edremit Bay, Northern Aegean Sea, Türkiye

Edremit Bay is one of the important areas for small–scale fishing in the North Aegean Sea. For this reason, more detailed ichthyoplankton studies should be continued to evaluate the fish stock status of the region, calculate the adult fish biomass, and determine the spawning period, place, and time of fish species. In addition, from 2011 to 2013, artificial reefs were constructed in Edremit Bay. Regular investigation of fish eggs and larvae in the region influenced by the Edremit Bay artificial reef would provide better knowledge of the structure and function of the local ecosystem and provide a basis for monitoring the marine ecosystem in the area. The current research examined the species abundance and distribution of surface plankton samples collected in 2015 and 2016. The evaluation also included the influence of abiotic environmental factors such as temperature, pH, chlorophyll a (chl–a), salinity, depth, and dissolved oxygen. Throughout the research, 3345 eggs and 176 larvae were analyzed. 57 species of eggs and larvae were identified. Eggs were not found in the natural reef (S3) in the summer and winter of 2015, while the highest egg abundance (212.83·100 m-3) was recorded in the natural reef (S1) in the summer of 2016. Larvae were not found in the natural reefs (S2 and S3) in the summer, autumn and winter of 2015 and in the artificial reefs (S4 and S5) in the summer and autumn in 2015 while the highest larvae abundance (8.12·100 m-3) on the artificial reef (S1) in summer 2016. Although the natural reefs had the highest number of species (30 species), the artificial reefs showed the lowest species diversity (17 species).

Population dynamics of spotted scat, Scatophagus argus (Linnaeus 1766) from the Sundarbans of Bangladesh

In Bangladesh, the mangrove areas of the Sundarbans are a hotspot for the spotted scat (Scatophagus argus), as the estuarine tributeries are significant zones for fishing, local marketing and foreign trading. Due to the widespread capture of spotted scats in the wild for a variety of uses, parameters of population were estimated using length-frequency and body weight data gathered from various sites in the southwestern forest areas of the country to comprehend the stock's status. Between May 2022 and April 2023, 1280 S. argus individuals were sampled from Khulna, Bagerhat and Satkhira. To gain insight into the population dynamics of S. argus, estimations of the growth parameters, recruitment pattern, mortalities, and level of exploitation (E) were made. For S. argus, a bit of negetive allomentric growth (b = 2.95) was observed. Moreover, the growth performance index (φ′), the asymptotic length (TL∝) and the growth coefficient (K) were 2.83, 34.65, cm and 0.56 yr−1, respectively. Natural mortality (1.08 yr−1) was lower than fishing mortality (1.12 yr−1). In the wild, this species recruits throughout the year, reaching its peak between October and January. By fishing gear, 50 % of the S. argus were caught between 7.71 cm and 9.43 cm. Moreover, high fishing mortality was assumed in both the small group (11–15 cm) and the large group (29–33 cm) of S. argus by virtual population analysis (VPA). It was discovered that the E for S. argus was 0.51, over the maximum permissible limit (Emax = 0.48). In summary, it is discovered that the S. argus population is overexploited. Therefore, in order to preserve this popular fish species and avoid local extinction, spotted scat resources should be taken into account under appropriate fisheries management guidelines. These findings will guide policymakers to manage the species accordingly.

Management strategy evaluation operating model conditioning: a swordfish case study

Evaluation of fish stock status is a key step for fisheries management. Tuna Regional Fisheries Management Organizations (t-RFMOs) are moving towards management strategy evaluation (MSE), a process that combines science and policy and depends on technical aspects, developed by scientists, designed to meet management objectives established by managers and other stakeholders. In the Indian Ocean, the current management advice for swordfish (Xiphias gladius) is based on an ensemble of 24 models considering four areas of uncertainty about the stock dynamics. There is an ongoing MSE process for swordfish, and this paper describes the methodology being applied for the conditioning of the operating model (OM), including model selection and validation. In the MSE, nine sources of uncertainty were considered, each being characterized by 2–3 levels. A partial factorial design was employed to reduce the number of models from a full factorial design to those needed to encompass the overall uncertainty. A selection and validation process was carried out, filtering models that converged, showed good predictive skills, and provided plausible estimates. Overall, the estimated spawning stock biomass (SSB) relative to SSB at maximum sustainable yield (MSY), and fishing mortality (F) relative to FMSY encompasses the estimates of the stock assessment ensemble at the most optimist area of the distribution. The MSE for swordfish is an ongoing process that is expected to provide more robust management advice in the future. Further developments to the OM can still occur, but the methods presented herein can be applied to this, or other species, MSE processes.

Non-model method for the stock status assessing and catch forecasting of the Flounder 26+28 subdivisions ICES in the Baltic Sea

The aim of this article: to assess the flounder stock state in the 26+28 ICES subdivisions of the Baltic Sea and forecast its catch in the Russian part of the 26th ICES subdivision using non-model methods.Methods used: The qualitative condition of the stock was assessed by length (LBI method — Length Based Indicators). To develop catch recommendations for flounder stock in 26+28 ICES subdivision, as well as in the Russian sea area, was used an approach for a stock category 3 (ICES classification), based on a combined biomass index for fish from bottom trawl surveys. The assessment was based on the ratio of the average values of population indices of the last two years to the previous values for three years. All methods have been successfully tested at the international level within the framework of seminars and Working Groups of the International Council for the Exploration of the Seas (ICES), in which Russian specialists took part.Novelty: In conditions of insufficient completeness and quality of available information to justification the flounder catch, using models of the exploited stock, for the Russian water area of the 26th ICES subdivision of the Baltic Sea, non-model methods for assessing the state and predicting its catch were used for the first time. Result: to solve problems of rational management and conservation of fish stocks, the LBI method, as a non-model assessment tool, allows timely identification of qualitative changes occurring in the stock. The flounder stock is within biologically safe limits. The fishery is aimed at preserving small and large fish (conservation option), the stock is exploited optimally. It is possible to maintain the species’ production level at least at the current level.Practical significance: In modern conditions the current level of information support for forecasting the flounder stock state and catch in the Baltic Sea will make it possible to solve problems related to the management of this resource in the near future.

Social-ecological Factors, Stock Status, and Governance Relating to a Shellcraft Fishery in the Indo-Pacific Region

Shellcraft is a livelihood activity that utilizes shells and skeletal remains of marine taxa for producing ornamental and decorative items. Despite an increasing importance of shellcraft in coastal areas of the Indo-Pacific region, information necessary for stakeholders to identify and respond to change through policy and management decisions is often lacking for fisheries that support this activity. To address this knowledge gap, a quantitative approach was taken to evaluate social-ecological factors (the what, where, how much, who, when, how, how often, and how long) in a “shellcraft fishery” centered at the Nusa Islands of Papua New Guinea. More than 151,100 individuals across 69 marine taxa were fished annually for shellcraft at the Nusa Islands; fishing was infrequent and quantities fished were low for most taxa when compared with other small-scale fisheries. Fishing most taxa had no association with the main demographic divisions within households although, in terms of participation and catch richness, women were the main actors. Gleaning, combing, and free-diving were the only fishing techniques used, with taxa primarily fished by gleaning intertidal habitats during the day. To contextualize sustainability of this fishery, local ecological knowledge-based perceptions of stock status for the marine taxa fished were examined. Considerations for governance, which included synthesis of existing regulatory measures and aspirations, are also discussed. Since shellcraft occurs throughout the Indo-Pacific region and there are commonalities in taxa utilized, this study provides a basis for comparative analysis of shellcraft fisheries within the region.

AI-powered Real-time Agricultural Produce Monitoring System for Improved Inventory Management and Market Efficiency in Oman

The agricultural sector in Oman faces challenges in accurately tracking and managing produce quantities in real-time across geographically dispersed locations. This research introduces the CBMIS, an AI-powered Real-time Agricultural Produce Monitoring System. The CBMIS leverages the Internet of Things (IoT) and biometric authentication to capture weight data from farms. This data is then transmitted to a cloud server, providing stakeholders with immediate access to variety-wise stock status. By utilizing AI, the CBMIS can go beyond simple data collection. AI can analyze historical data and market trends to predict future production levels and market demands. This real-time information empowers stakeholders to make informed decisions regarding logistics, sales, and marketing strategies. The CBMIS has the potential to improve inventory management, optimize resource allocation, and enhance overall market efficiency within the Omani agricultural sector.

Within-well patterns in bigeye tuna catch composition and implications for purse-seine port-sampling and catch estimation for the Eastern Pacific Ocean

In response to concerns about the stock status of bigeye tuna (BET) in the Eastern Pacific Ocean, the Inter-American Tropical Tuna Commission adopted additional management measures for BET in 2021, including an individual-vessel catch threshold system for the purse-seine fishery. Development of an enhanced port-sampling program for estimation of trip-level BET catch was also mandated to support member countries and their purse-seine vessels in their conservation efforts. To this end, a pilot study was conducted in the ports of Manta and Posorja, Ecuador, in 2022. In these ports, well unloading often takes place with small containers, which are used to transport fish from inside the well to the vessel’s wet deck. Using a high-frequency systematic sampling protocol, 63 wells of 37 trips with catch exclusively from floating-object (OBJ) sets were sampled from the start to the end of unloading, at a fixed interval from a random starting point, sampling about 10 % of all the containers of fish unloaded from each well. Notable large-scale pattern in the proportion of BET per container was found for 38 of the 56 wells that had BET catch. The proportion of BET per container, which could be high at the beginning, middle or end of the well unloading, sometimes varied by 0.40 or more. The magnitude of this large-scale within-well pattern had a significant increasing relationship with the number of OBJ sets associated with the well catch, consistent with variability in species composition among OBJ sets being an important factor in determining variability in species composition during catch unloading. Simulation studies demonstrated that such large-scale within-well pattern has potential implications for OBJ-set well-level sampling design, where, as expected from sampling theory, a systematic sampling protocol for containers of fish generally resulted in lower mean squared error (MSE) on the proportion of BET in the well, compared to simple random sampling of containers of fish. The reduction in MSE was largely due to a reduction in variance. Simulations also showed that the within-well variance component of the trip-level estimator for the proportion of BET can be larger than the among-well variance component, unless the within-well sampling coverage is relatively high. To minimize the negative impact of within-well variability on the precision of the estimator, results indicate that for a sampling protocol with one systematic sample per well, the within-well coverage should be at least 2 % of containers of fish unloaded from the well, and preferably more than 3 %. Finally, simulation studies were conducted with observer well plan data from 2013 to 2022 to put the well-level results in a larger context. Results indicated that the level of within-well sampling coverage may affect the variance on fleet-level estimates of the proportion of BET in the catch, with potentially substantially higher variance when the within-well sampling coverage is low. Taken together, these results suggest that both the type of within-well sampling and the level of within-well sampling coverage have important implications for the variance on BET catch estimates, from the well level to the fleet level.

Spatial and seasonal variations in the growth of the populations of tongue sole fish (Cynoglossus quadrilineatus Bleeker, 1851) along four different stations of Makran coast by using the von Bertalanffy model

BackgroundGrowth is a most important life-history trait that defines the maximum size and age, maturation stage, and mortality of any fish species and is also involved in stock assessment models commonly used in fisheries conservation or management. ObjectivesThe present study focused on assessing the growth patterns and related parameters to the population of tongue sole (Cynoglossus quadrilineatus) along different sites of the Makran coast in temperate regions. MethodologyA total of 987 tongue sole fishes were collected seasonally from four different sites along the Makran coast (Gwadar, Pasni, Ormara, and Sur Bandar). Growth parameters i.e., length-weight relationships, length-frequency distribution, von Bertalanffy (VBGF) growth model, and stock status were analyzed. ResultsThe overall results of the length-weight relationship (LWRs) of this species showed only a significantly positive allometric growth pattern (b < 3.0; p < 0.05) observed during three seasons along the four selected sites of Makran Coast. The estimated von Bertalanffy (VBGF) growth parameters of C. quadrilineatus at four stations were described as; maximum observed length (Lmax) = 31.65 cm, asymptotic length (L∞) = 33.32 cm, size at sexual maturity (Lm) = 17.98 cm, Lopt = 20.55 cm, growth coefficient per year (k) = 0.55 year -1, t0 = 0.04 year -1, f = 2.79, Tmax = 2.80 years, tm = 0.78 year, M = 1.64 per year, topt = 1.30 years. The present study also noted seasonal variations in the length frequency distribution (LFD) data between the four selected sites. ConclusionsThus, our study concluded that the von Bertalanffy growth model (VBGF) is the best-fitted model for analyzing the growth patterns of C. quadrilineatus at different sites and during various seasons along the Makran Coast. This model demonstrated superior predictive ability and effectively described changes in growth patterns or body size across sub-populations of C. quadrilineatus at the four study sites. Thus, our research provides valuable insights into the population dynamics and life history traits of this tongue sole population in the Makran coast. Moreover, as the first study on the growth of this species, our findings offer essential information for informing sustainable exploitation, conservation, and fishery management strategies.

Fishers' ecological knowledge points to fishing-induced changes in the Peruvian Amazon.

Scientists increasingly draw on fishers' ecological knowledge (FEK) to gain a better understanding of fish biology and ecology,and inform options for fisheries management. We report on a study of FEK among fishers along the Lower Ucayali River in Peru, a region of exceptional productivity and diversity, which is also a major supplier of fish to the largest city in the Peruvian Amazon. Given a lack of available scientific information on stock status, we sought to identify temporal changes in the composition and size of exploited species by interviewing fishers from 18 communities who vary in years of fishing experience since the mid-1950s. We develop four FEK-based indicators to assess changes in the fish assemblage and compare findings with landings data. We find an intensification of fishing gear deployed over time and spatiotemporal shifts in the fish assemblage and reported declines in species weight, which point to a fishing-down process with declines across multiple species. This finding is reflected in a shifting baseline among our participants, whereby younger generations of fishers have different expectations regarding the distribution and size of species. Our study points to the importance of spillover effects from the nearby Pacaya-Samira National Reserve and community initiatives to support the regional fishery. Reference to fishers' knowledge also suggests that species decline is likely underreported in aggregated landings data. Despite the dynamism and diversity of Amazonian floodplain fisheries, simple FEK-based indicators can provide useful information for understanding fishing-induced changes in the fish assemblage. Fishers hold valuable knowledge for fishery management and conservation initiatives in the region.

Growth parameters and stock assessment of Carangoides bajad Forsskal, 1775 (Carangiformes: Carangidae) in Jeddah fisheries

ABSTRACT The stock status of Carangoides bajad in Jeddah fisheries was assessed by estimating the growth parameters, mortality rates and size at first capture (Lc), then applying the results to estimate the yield and biomass per recruit. The length-weight relationship could be described by the power equation: W = 0.011 L3.019 (R2 = 0.99) for combined sexes. Von Bertalanffy Growth Parameters L∞, K and t0 were estimated to be 71.53 cm, 0.224 year −1, and −0.52 year, respectively. The total, natural, fishing mortality coefficients and exploitation were calculated to be 0.72 year −1, 0.337 year −1, 0.383 year −1, and 0.53 year −1, respectively. Beverton and Holt (1957) model was used to estimate the yield and biomass per recruit at Fcur and Lc and found to be Y/R = 291 g and B/R = 759 g. Compared with the two biological reference points Fmax = 0.56 year −1 and F0.1 = 0.346 year −1, the Fcur value was very close to the F0.1 value required to get the optimum Y/R. We recommend avoiding any increase in Fcur, and increasing Lc to be 38 centimetres to increase the B/R from 759 g to 793 g, which would increase the probability of sustaining sufficient recruitment to the fishery of C. bajad in Jeddah fisheries.

Developing management plans for sprat (Sprattus sprattus) in the Celtic Sea to advance the ecosystem approach to fisheries

Sprat are commercially valuable and are an important component of the North-East Atlantic ecosystem as major predators of zooplankton, competitors with herring, and prey for piscivorous fish, marine mammals, and seabirds. Despite this, insufficient information exists for Celtic Seas sprat, one of five North-East Atlantic stocks, to estimate stock status. To ensure the sustainable exploitation of sprat, the health of the Celtic Seas ecosystem, and the wider fisheries sector, we conduct a management strategy evaluation to stress test the current single-species advice framework. The aim is to evaluate whether ecosystem objectives can be achieved under single-species maximum sustainable yield and precautionary advice frameworks. An operating model was conditioned on life history theory and strategic information from ecosystem models. We showed that in-year advice using an empirical rule could achieve management objectives and help balance the trade-offs between fishing activities and ecosystem health. The approach allows ecosystem understanding to be incorporated within existing precautionary and maximum sustainable yield frameworks to provide a robust management framework that can meet multiple objectives despite uncertainty.