Target Catch Research Articles

Reducing sea turtle bycatch with net illumination in an Indonesian small-scale coastal gillnet fishery

Small-scale fisheries are economically and culturally important throughout the world’s coastal waters. These fisheries, however, often have high bycatch rates of protected marine species. Bycatch in small scale gillnet fisheries is thought to be a major driver behind the declines of several sea turtle populations. Recent studies addressing this issue have identified net illumination as a potentially effective bycatch reduction technology (BRT) to reduce sea turtle interactions with gillnet fisheries. In Southeast Asia, small-scale gillnet fisheries make up a large components of fishing effort often in areas that overlap with important sea turtle habitat. We conducted controlled experiments of net illumination as a potential BRT to reduce sea turtle bycatch in a coastal gillnet fishery based in Paloh, West Kalimantan, Indonesia. Results indicated that net illumination significantly reduced multi-species sea turtle bycatch by 61.4% and specifically green sea turtles (Chelonia mydas) by 59.5%, while the CPUE of total catch and target species remained similar. Moreover, this study suggests that Indonesian fishers can increase their overall market value when using net illumination as the market value per unit effort (MVPUE) of both the total catch and target catch showed significant increases. These results suggest that net illumination could be an effective sea turtle conservation tool for small-scale coastal gillnet fisheries in Indonesia and potentially throughout Southeast Asia. In addition, data from the control treatments of this study also provided the first observer based sea turtle bycatch estimate for a small-scale gillnet fishery in Southeast Asia. Challenges to the broad scale implementation of net illumination to reduce this bycatch of sea turtles include the cost, availability of the technology, socialization of the BRT to fishers, and government interest and support for net illumination as a tool for bycatch reduction.

A Comparison of Circle and J Hook Performance Within the Grenadian Pelagic Longline Fishery

The use of circle hooks in pelagic longline fisheries has often been proposed as a minimally disruptive means to minimize bycatch mortality. However, most studies have been in large scale fisheries, not the small-vessel fleets seen in many Caribbean countries. Size 16/0 circle hooks and 9/0 J hooks were alternated over 26 sets to assess the performance of circle hooks in the Grenadian pelagic longline fishery. Catch, mortality, hook location, length, and grade of fish were compared between hook types. No species-specific differences in at-vessel mortality rate or yellowfin tuna grade were found between hook types. However, significantly fewer billfish collectively (t = 2.36, p = 0.028), and sailfish specifically (t = 3.04, p = 0.005), were caught on circle hooks. Additionally, tunas caught with circle hooks had a 69% greater chance of external hooking compared to J hooks (χ2 = 4.38, p = 0.036). All other species analyzed had similar catch rates regardless of hook type (p < 0.05), including yellowfin tuna. The results of this study suggest that the Grenadian pelagic longline fishery – and other Caribbean fleets, by extension – could reduce impacts on billfish stocks by using 16/0 circle hooks without incurring negative effects on yellowfin tuna catch rate or grade. With many bycatch species populations at depressed levels, these results also provide further evidence that circle hooks should be the recommended terminal gear type when using a bycatch mitigation approach to manage pelagic longline fisheries while maintaining target catches for local and export markets.

SMART Drumlines Ineffective in Catching White Sharks in the High Energy Capes Region of Western Australia: Acoustic Detections Confirm That Sharks Are Not Always Amenable to Capture.

Simple SummaryShark hazard mitigation measures are often introduced after human-shark interactions, which are increasing. Such measures are often contentious, and care is needed to reduce the risk to ocean users without causing negative ecosystem impacts. Here, we examined the effectiveness of Shark-Management-Alert-in-Real-Time (SMART) drumlines to catch, tag, relocate and release white sharks (Carcharodon carcharias) in the Capes region of Western Australia. The project aimed to examine the movement patterns of white sharks’ post-release to determine whether their relocation provided a reduction in risk for ocean users. The effectiveness of the program was also evaluated in terms of minimising the mortality of all animals caught. In total, 352 fish were caught over the 27-month trial period and 91% of animals were released alive in good condition. Only two white sharks (target species) were caught, both of which moved immediately offshore after capture and remained predominantly in offshore waters for the duration of tag deployment. The detection of 24 other tagged white sharks within the acoustic array during the trial period confirms that the target species were not always amenable to capture. Our results reiterate there is no simple remedy for dealing with the complexities of shark hazards and reinforce the importance of trialing mitigation measures under local conditions.The management of human-shark interactions can benefit from the implementation of effective shark hazard mitigation measures. A Shark-Management-Alert-in-Real-Time (SMART) drumline trial in the Capes region of Western Australia was instigated after several serious incidents involving surfers and white sharks (Carcharodon carcharias). The project aimed to determine whether white sharks (target species), which were relocated after capture, remained offshore using satellite and acoustic tagging. Over a 27-month period, 352 fish were caught, 55% of which comprised tiger sharks (Galeocerdo cuvier). Ninety-one percent of animals were released alive in good condition. Only two white sharks were caught; both were relocated ≥ 1 km offshore before release and moved immediately further offshore after capture, remaining predominately in offshore waters for the duration of their 54-day and 186-day tag deployments. Our results confirm that desirable animal welfare outcomes can be achieved using SMART drumlines when response times are minimised. The low target catches and the detection of 24 other tagged white sharks within the study area supported the decision to cease the trial. Our results reiterate there is no simple remedy for dealing with the complexities of shark hazards and reinforce the importance of trialing mitigation measures under local conditions.

What’s the catch? Examining optimal longline fishing gear configurations to minimize negative impacts on non-target species

Changes to fishing gear configurations have great potential to decrease fishing interactions, minimize injury and reduce mortality for non-target species in commercial fisheries. In this two-part study, we investigate potential options to optimize fishing gear configurations for United States Pacific pelagic longline vessels to maintain target catch rates whilst reducing bycatch mortality, injury, and harm. In part one, a paired-gear trial was conducted on a deep-set tuna longline vessel to compare catch rates and catch condition of target and non-target species between wire and monofilament leader materials. Temperature-depth recorders were also deployed on hooks to determine sinking rates and fishing depth between the two leader materials. In part two, hooks of different configurations (size, diameter, shape, metal type, and leader material) were soaked in a seawater flume for 360 days to obtain quantitative estimates of breaking strength, as well as the time taken for gear to break apart. We found that switching from wire to monofilament leaders reduced the catch rate of sharks by approximately 41 %, whilst maintaining catch rates of target species (Bigeye tuna, Thunnus obesus). However, trailing gear composed of monofilament did not break apart even after 360 days. In contrast, branchlines with wire leaders began to break at the crimps after approximately 60 days. Additionally, the breaking strength of soaked fishing hooks was greater for larger, forged hooks composed of stainless steel typically used in United States Pacific longline fisheries. These results have direct implications for fisheries management and the operational effectiveness of bycatch mitigation strategies for longline fisheries worldwide.

Bycatch and discards in the artisanal shrimp trawl fishery in Northern Peru.

This study analyses the bycatch composition of an artisanal shrimp trawl fleet operating between Cabo Blanco and Máncora in Northern Peru between April 2019 and March 2020. A total of 300 hauls were analysed with respect to target catch and bycatch (consisting of other commercial species, discards, and macroalgae). A total of 277 species were recorded including 111 species of fish, 65 species of molluscs, 51 species of crustaceans, 22 species of algae, 12 species of cnidarian, 9 species of echinoderms, 4 species of Bryozoa and 3 species of polychaeta. Capture per unit effort (CPUE, kg.h-1) was highest for fish, followed by crustaceans, algae and molluscs. The target species Penaeus californiensis coffee shrimp constituted 17.8% of the overall catch,82.2% represented bycatch, and 50.6% represented discards. Coffee shrimps were more abundant in June and November 2019 and in January and February 2020. Highest bycatch CPUE occurred in May, June and December 2019. The most abundant species in the bycatch throughout the study period were sand perch (Diplectrum conceptione, 16% weight of the total catch), the macroalgae caulerpa (Caulerpa filiformis, 13%), sole flounder (Etropus ectenes, 6.4%), Pacific drum (Larimus pacificus, 5.7%), and lumptail searobin (Prionotus stephanophrys, 5.1%). Overall, the contribution of sand perch and flounder, exceeded the weight of coffee shrimp, therefore the interpretation that shrimp is the sole target species needs to be revised. The number of discarded species per month increased towards the spring months with the highest value in November. This study represents the first characterisation of bycatch in the artisanal trawling fishery in the Piura region in northern Peru and reveals a high proportion of bycatch in the fishery but also hints at potential temporal management measures that could be imposed to reduce the levels of bycatch. For example, the months of May and December had the greatest bycatch to shrimp ratios and the fishery could potentially be closed to avoid high bycatch risk, however, longer term information is needed to assess if the trends observed in bycatch are similar over longer periods of time. The species characterisation of bycatch also provides information for the design of modified nets which would target the reduction of small fish present in the catch.

Effect of ground gear modification on bycatch of rays in mediterranean bottom trawl fishery

Bycatch of rays and skates in towed fishing gears represents one of the major threats to these relatively slow-growing marine species. The objective of this study was to modify ground gear in a bottom trawl fishery to increase the escape of these species during towing without associated loss of target catch. Sea trials were carried out with a research vessel in Mersin Bay, North-eastern Mediterranean. Experimental ground gear was modified by cutting the rigging twine between the fishing line and the footrope in the central part of the ground gear. Capture of three unwanted bycatch species were estimated. The probability of capture of guitarfish (Rhinobatos sp.) and common stingray (Dasyatis pastinaca) was significantly reduced to 8% and 20% for guitarfish and stingray, respectively compared to standard ground gear. The results for spiny butterfly ray (Gymnura altavela) were inconclusive due to the wide confidence intervals. Further, the catch comparison results for five out of six target species investigated did not show significant reduction in catch efficiency when using experimental gear compared to the standard trawl. Only for common sole (Solea solea) the modified trawl had significantly lower catch efficiency than the standard trawl. We believe that this technical measure for reducing unwanted bycatch in bottom trawls has a potential to be adopted by the fishery due to being an efficient, low-cost measure which does not create additional challenges during handling of the gear.

Barriers to Achieving Conservation Engineering Goals in Commercial Trawl Fisheries

The advancement of conservation practices in global trawl fisheries has been impeded in part by a lack of a collective understanding of the most relevant and broad-scale knowledge-needs, along with the identification of potential barriers to addressing these knowledge-needs. Using both an online survey and an in-person workshop, we engaged a diversity of fishing industry stakeholders including scientists, technology companies, trawl net makers, and fishermen working with North Pacific, United States, trawl fisheries to identify and prioritize areas in which further knowledge is required for successful implementation of conservation engineering practices. In addition, we identified barriers to addressing these knowledge-needs. Knowledge-needs related to fishing gear performance were identified among the top priorities, including several areas targeted at improving fishing efficiency that could further advance the sustainability of well-managed trawl fisheries. To better understand the composition and behavior of target versus non-target catch, workshop participants identified the importance of closing data and technology gaps. This highlights areas for potential collaboration between fishermen, researchers, and technology companies to address research prioritized by the end-user. Further, results from the workshop emphasized a need for industry-driven training and workshops focused on elevating fishermen skill for newer entrants through peer-learning and knowledge-sharing to achieve objectives like better non-target avoidance and increased fishing efficiency of the target species. Addressing these prioritized knowledge-needs, by first working toward overcoming the industry-identified barriers, may aid in increasing uptake of conservation practices, thereby contributing to the long-term sustainability of these fisheries and associated social-ecological systems.

Trade-offs between bycatch and target catches in static versus dynamic fishery closures

While there have been recent improvements in reducing bycatch in many fisheries, bycatch remains a threat for numerous species around the globe. Static spatial and temporal closures are used in many places as a tool to reduce bycatch. However, their effectiveness in achieving this goal is uncertain, particularly for highly mobile species. We evaluated evidence for the effects of temporal, static, and dynamic area closures on the bycatch and target catch of 15 fisheries around the world. Assuming perfect knowledge of where the catch and bycatch occurs and a closure of 30% of the fishing area, we found that dynamic area closures could reduce bycatch by an average of 57% without sacrificing catch of target species, compared to 16% reductions in bycatch achievable by static closures. The degree of bycatch reduction achievable for a certain quantity of target catch was related to the correlation in space and time between target and bycatch species. If the correlation was high, it was harder to find an area to reduce bycatch without sacrificing catch of target species. If the goal of spatial closures is to reduce bycatch, our results suggest that dynamic management provides substantially better outcomes than classic static marine area closures. The use of dynamic ocean management might be difficult to implement and enforce in many regions. Nevertheless, dynamic approaches will be increasingly valuable as climate change drives species and fisheries into new habitats or extended ranges, altering species-fishery interactions and underscoring the need for more responsive and flexible regulatory mechanisms.

Hand dredging for the wedge clam (Donax trunculus) in the Algarve coast (southern Portugal): fishing yield, bycatch, discards and damage rates

ABSTRACT This study aimed to characterize the catches, quantify fishing yield, bycatch and discards, and also estimate damage and mortality rates using hand dredges with two different mesh sizes (20 and 25 mm) for harvesting the wedge clam (Donax trunculus). A total of 160 tows were performed in Lota Beach and Armona Island in the Algarve coast (southern Portugal). Overall, were caught 12,319 individuals (3985 in Lota Beach and 8334 in Armona Island) belonging to 48 taxa distributed among seven phyla (14 taxa in Lota Beach and 44 taxa in Armona Island). Bycatch proportions ranged from 13.1% to 32.0% in abundance and from 10.7% to 32.9% in biomass, with more bycatch using hand dredges with 20 mm mesh size. Commercially undersized D. trunculus (MCRS = 25 mm SL) prevailed within the bycatch, representing over 40% of discards using both mesh sizes. Due to different size selectivity, the target catch (CPUE) and bycatch per unit effort (BCPUE) in abundance and biomass, as well as fishing yield as a function of tow duration and towed area, were lower for hand dredges with 25 mm mesh than with 20 mm mesh. In general, damage and mortality rates were fairly low (1.3–2.6%) independently of mesh size, reinforcing the importance of releasing live bycatch to the sea immediately after sorting the catches. Overall, this study prompted the need to develop a good practice guide for hand dredgers, aiming to mitigate avoidable indirect discards mortality and improve the sustainability of this traditional harvesting activity.

Area‐based management of blue water fisheries: Current knowledge and research needs

AbstractThe pelagic fisheries beyond the continental shelves are currently managed with a range of tools largely based on regulating effort or target catch. These tools comprise both static and dynamic area‐based approaches to include gear limitations, closed areas and bycatch limits. There are increasing calls for additional area‐based interventions, particularly expansion of marine protected areas, with many now advocating closing 30% of the oceans to fishing. In this paper, we review the objectives, methods and successes of area‐based management of blue water fisheries across objectives related to food production and environmental, social and economic impacts. We also consider the methods used to evaluate the performance of area‐based regulations and provide a summary of the relative quality of evidence from alternative evaluation approaches. We found that few area‐based approaches have been rigorously evaluated, and that it is often difficult to obtain requisite observational data to define a counterfactual to infer any causal effect for such evaluation. Management agencies have been relatively successful at maintaining important commercial species at or near their target abundance, but success at meeting ecological or social goals is less clear. The high mobility of both target and bycatch species generally reduces the effectiveness of area‐based management, and shifting distributions due to climate change suggest that adaptive rather than static approaches will be preferred. We prioritize research and management actions that would make area‐based management more effective.

A Deep Learning Approach to Assist Sustainability of Demersal Trawling Operations

Bycatch in demersal trawl fisheries challenges their sustainability despite the implementation of the various gear technical regulations. A step towards extended control over the catch process can be established through a real-time catch monitoring tool that will allow fishers to react to unwanted catch compositions. In this study, for the first time in the commercial demersal trawl fishery sector, we introduce an automated catch description that leverages state-of-the-art region based convolutional neural network (Mask R-CNN) architecture and builds upon an in-trawl novel image acquisition system. The system is optimized for applications in Nephrops fishery and enables the classification and count of catch items during fishing operation. The detector robustness was improved with augmentation techniques applied during training on a custom high-resolution dataset obtained during extensive demersal trawling. The resulting algorithms were tested on video footage representing both the normal towing process and haul-back conditions. The algorithm obtained an F-score of 0.79. The resulting automated catch description was compared with the manual catch count showing low absolute error during towing. Current practices in demersal trawl fisheries are carried out without any indications of catch composition nor whether the catch enters the fishing gear. Hence, the proposed solution provides a substantial technical contribution to making this type of fishery more targeted, paving the way to further optimization of fishing activities aiming at increasing target catch while reducing unwanted bycatch.

Reproductive hyperallometry and managing the world’s fisheries

Marine fisheries are an essential component of global food security, but many are close to their limits and some are overfished. The models that guide the management of these fisheries almost always assume reproduction is proportional to mass (isometry), when fecundity generally increases disproportionately to mass (hyperallometry). Judged against several management reference points, we show that assuming isometry overestimates the replenishment potential of exploited fish stocks by 22% (range: 2% to 78%) for 32 of the world's largest fisheries, risking systematic overharvesting. We calculate that target catches based on assumptions of isometry are more than double those based on assumptions of hyperallometry for most species, such that common reference points are set twice as high as they should be to maintain the target level of replenishment. We also show that hyperallometric reproduction provides opportunities for increasing the efficacy of tools that are underused in standard fisheries management, such as protected areas or harvest slot limits. Adopting management strategies that conserve large, hyperfecund fish may, in some instances, result in higher yields relative to traditional approaches. We recommend that future assessment of reference points and quotas include reproductive hyperallometry unless there is clear evidence that it does not occur in that species.

Data Poor Approach for the Assessment of the Main Target Species of Rapido Trawl Fishery in Adriatic Sea

Information on stock status is available only for a few of the species forming the catch assemblage of rapido fishery of the North-central Adriatic Sea (Mediterranean Sea). Species that are caught almost exclusively by this gear, either as target (such as Pectinidae) or accessory catches (such as flatfishes apart from the common sole), remain unassessed mainly due to the lack of data and biological information. Based on cluster analysis, the catch assemblage of this fishery was identified and assessed using CMSY model. The results of this data-poor methodology showed that, among the species analyzed, no one is sustainably exploited. The single-species CMSY results were used as input to an extension of the same model, to test the effect of four different harvest control rule (HCR) scenarios on the entire catch assemblage, through 15-years forecasts. The analysis showed that the percentage of the stocks that will reach Bmsy at the end of the projections will depend on the HCR applied. Forecasts showed that a reduction of 20% of fishing effort may permit to most of the target and accessory species of the rapido trawl fishery in the Adriatic Sea to recover to Bmsy levels within 15 years, also providing a slight increase in the expected catches.

Evidence on Otolith Structure and some Ecological Features of Three Small Foraging Species along the Southern Black Sea Coast

In this study, we aimed to describe otoliths to provide information about the stomach contents of three small foraging species and to contribute to the currently limited biological and ecological evidence about the species. Seasonal experimental bottom trawl surveys were conducted along the shelf areas of the Kızılırmak-Yeşilırmak and Melet Rivers to collect investigation materials which were abundant in the bycatch composition of the target catch. The information about body size measurements, abundance values, depth, season, and locality of samplings was recorded for further evaluations. Otolith shapes were defined as discoidal to ovate for the Aphia minuta, discoidal for the Pomatoschistus marmoratus, and square for the Arnoglossus kessleri. The mean length and weight values of the Aphia minuta, which was abundant along shallow coastal waters (0-30 m), were significantly different between localities and sampling season, but no difference was found between depth ranges. Pomatoschistus marmoratus, whose distribution varied significantly between depths and seasons had dense distributions along with the depth range of 30-60 m. Arnoglossus kessleri was most abundant along with the depth range of 0-30 m and had no samples in depths of over 60 m. It was found that the mean values of length and weight of this species were only significantly different among seasons but similar over the depth ranges and localities.

Socio-ecological approach on the fishing and trade of rhino rays (Elasmobranchii: Rhinopristiformes) for their biological conservation in the Bay of Bengal, Bangladesh

Rhinopristioid rays are among the most globally threatened cartilaginous fishes, almost all of which are Critically Endangered. Fishery pressure and lack of knowledge, especially where these elasmobranch fish overlap their habitats off developing countries in the Indo-West Pacific, impede their biological conservation which in turns result in unnoticed population depletion. Rhino rays are an important component of the Bangladeshi artisanal fishery; however, an understanding of these fisheries and their trade is limited. Fishers and traders were interviewed between June 2018 and June 2019 in four areas of southeast Bangladesh to characterize rhino ray fishing, trade and fishers' perception of population trends. All interviewed fishers reported life-long rhino ray catch in sizable numbers and noted a steep decline in the catch over time, especially for Rhynchobatus spp. Seven species were documented- not only targeted by un-baited longlines but also by-caught in gillnets and set-bag nets. Unregulated and undocumented catch fuelled by substantial international trade to Myanmar on high-quality skin, meat and fins; and national usages of meat, liver, cartilages and intestines. Between 9000 and 33000 kg (avg. 23000 kg) of rhino rays were bought annually by each trader during 2015–2018. Southcentral shallow-water char (sand island) areas are perceived as essential habitats, hence providing important fishing grounds. The predominant threats are overexploitation by unselective gear use, bottom trawling, target catch, international trade and source of protein and income. Compliance with international trade control treaties or the Bangladeshi law was low, with most fishers (78%) unaware of specific regulation regarding rhino rays. It is crucial to adopt precautionary principles to prevent further rhino ray population declines. We propose a combination of actions rooted in sustainability and inclusiveness in this regard; e.g. a) trade mitigation, monitoring and enforcement, b) need for sustainable fisheries management regimes, c) need for habitat protection; finally, d) the importance of fishers’ inclusiveness in conservation decision making.

Comparing Dynamic and Static Time-Area Closures for Bycatch Mitigation: A Management Strategy Evaluation of a Swordfish Fishery

Time-area closures are a valuable tool for mitigating fisheries bycatch. There is increasing recognition that dynamic closures, which have boundaries that vary across space and time, can be more effective than static closures at protecting mobile species in dynamic environments. We created a management strategy evaluation to compare static and dynamic closures in a simulated fishery based on the California drift gillnet swordfish fishery, with closures aimed at reducing bycatch of leatherback turtles. We tested eight operating models that varied swordfish and leatherback distributions, and within each evaluated the performance of three static and five dynamic closure strategies. We repeated this under 20 and 50% simulated observer coverage to alter the data available for closure creation. We found that static closures can be effective for reducing bycatch of species with more geographically associated distributions, but to avoid redistributing bycatch the static areas closed should be based on potential (not just observed) bycatch. Only dynamic closures were effective at reducing bycatch for more dynamic leatherback distributions, and they generally reduced bycatch risk more than they reduced target catch. Dynamic closures were less likely to redistribute fishing into rarely fished areas, by leaving open pockets of lower risk habitat, but these closures were often fragmented which would create practical challenges for fishers and managers and require a mobile fleet. Given our simulation’s catch rates, 20% observer coverage was sufficient to create useful closures and increasing coverage to 50% added only minor improvement in closure performance. Even strict static or dynamic closures reduced leatherback bycatch by only 30–50% per season, because the simulated leatherback distributions were broad and open areas contained considerable bycatch risk. Perfect knowledge of the leatherback distribution provided an additional 5–15% bycatch reduction over a dynamic closure with realistic predictive accuracy. This moderate level of bycatch reduction highlights the limitations of redistributing fishing effort to reduce bycatch of broadly distributed and rarely encountered species, and indicates that, for these species, spatial management may work best when used with other bycatch mitigation approaches. We recommend future research explores methods for considering model uncertainty in the spatial and temporal resolution of dynamic closures.

Red Sea fish market assessments indicate high species diversity and potential overexploitation

In many parts of the world, particularly remote and underdeveloped regions, reports of fisheries catch, effort, and landing data are limited. In order to implement effective fishing regulations to protect natural stocks, understanding fishing pressure, key target species, catch composition, and value of each species is vital. In regions where published data is limited, and the sampling of numerous small boats and landing sites is not feasible, fish market surveys represent an opportunity to obtain key fisheries data. This study therefore aims to obtain species-specific prices and market composition for fish landed in the central Red Sea by surveying local fish markets. We conducted 11 surveys at two major Red Sea fish markets to ascertain key fisheries metrics using market data as a proxy for catch data. Results indicate that a high proportion of the market composition is generated by 46 species from six family-level groups, Serranidae, Labridae, scarine labrids, Carangidae, Lethrinidae, and Lutjanidae, contributing to 87 % of the total market biomass. Species-specific values ranged from 4.50 USD/kg to 26.44 USD/kg, with market surveys highlighting the economic value of three local serranid species: Plectropomus pessuliferus marisrubri, Plectropomus areolatus and Variola louti, all valued at more than 25 USD/kg, and a labrid: Cheilinus undulatus, valued at 26.44 USD/kg. The Serranidae family represents 47 % of the total biomass and 55 % of the potential revenue in the market, while also indicating potentially overfished reefs due to the high occurrence of smaller species and undersized individuals of higher priced serranid species. Many of the high-valued serranids were below the size at sexual maturity. Target species exhibited small body size and decreasing abundance, potentially indicating a “shrinking baseline” scenario occurring in the Saudi Arabian artisanal coral reef fishery. These results indicate that introducing effective fisheries legislation and management is necessary for the longevity and sustainability of the reef-based fishery in the Saudi Arabian Red Sea. Implementing catch quotas, size limits, and seasonal restrictions are potential mechanisms that could be used to facilitate positive change within this vulnerable fishery.

Assessing ocean temperature’s role in fishery production

Ocean temperatures are increasing. Little work has been done to examine the effects that these changes will have on fishery production. The study at hand seeks to incorporate the influence of climate change into an established static bioeconomic fishery model. Stock biomass is approximated to be a function of sea surface temperature. Following a feasible generalized least squares regression using data from the Western and Central Pacific, the interaction between fishery effort and temperature is found to be statistically significant. From this model, various functional forms relating effort, catch, profit, and temperature are specified. In particular, a function that returns an effort requirement given a target catch level and temperature forecast is generated.The importance of these tools for fishery management is explored through application to Western and Central Pacific tuna fisheries. Recommendations for extensions into future research are made and the foundation for a model of efficient effort allocation across time and the entirety of a management area, given changing temperatures, is specified. The study has succeeded in establishing the statistically significant role that temperature plays in the fishery production function.

Kuzey Ege Denizi’nde kullanılan çapari takımlarının av kompozisyonu

In this study was carried out between April 2015 and January 2017 at 0-120 m depth areas where commercial fishermen were fishing in North Aegean Sea, Çanakkale coasts. In this study, it is aimed to determine the species composition of caught species in trotline fishing and to determine the target and non-target catch rates. 6 different trotline types were used. As a result of 174 catching operations 7210 individuals were catched in total. When the ratio of the target species in catching with the trotlines are evaluated, the trotlines within the fishing gears such as fish pots, trammel nets and longlines catch more of the target species.

Seagrass-associated fish species’ richness: evidence to support conservation along the south coast of Lombok Island, Indonesia

Abstract. Syukur A, Al-Idrus A, Zulkifli L. 2021. Seagrass-associated fish species’ richness: evidence to support conservation along the South Coast of Lombok Island, Indonesia. Biodiversitas 22: 988-998. The concept of seagrass conservation at a global scale tends to be less appropriate with regard to the environmental conditions at the regional and local scales, and thus, there is a need for scientific studies at the regional and local scales to support conservation measures. This research aimed to describe the importance of seagrass conservation based on the species richness of seagrass-associated fish. Data were collected from seven seagrass locations using surveys and observation. Data on the fish species present were collected with the gear used by small-scale fishermen to catch fish in the seagrass area and the surrounding waters. Data analysis was descriptive; the statistical analyses performed included calculation of the Shannon-Wiener index of diversity (H '), the Simpson evenness index (E), and the Morisita species richness index (D) as well as cluster analysis. All statistical analyses were performed in IBM SPSS Statistics 25. We found 104 fish species belonging to 38 families. Leiognathidae, Apogonidae, Clupeidae, Carangidae, Channidae, Sillaginidae, and Mullidae are families with high abundance, and 16 fish species have an abundance of individuals above the average value (192 individuals) of the total number of individuals (20,352). Meanwhile, 94.37% of the fish families are the target catch of small-scale fishermen (commercial fish). The diversity of fish species associated with seagrass in the study location is evidence of the survival of seagrass provision services at the local scale for fish. Therefore, scientific evidence of the species richness of fish, species yang domina, and its importance for small-scale fisheries at each seagrass bed in the study location can be used as a source of information for increasing and improving seagrass conservation efforts at the local scale.