Catch Weight Research Articles

Sampling Procedure for Establishing Criteria for Sea Urchin (Loxechinus albus) Proportion under the Legal Minimum Length of landings

Sea urchin (Loxechinus albus) is one of the most economically important species in the northeast of Chilean Patagonia, forming part of the highly diverse benthic community. This resource is being harvested under selective fishing pressure, which suppresses growth rates. In response, the National Standards Institute established Regulation 44 as a quality control measure, based on a sampling approach considering the percentage of sea urchin under the minimum legal size (UMLS) through an acceptance sampling plan. In 2019, the Chilean Undersecretary of Fisheries and Aquaculture (SUBPESCA), under Exempt Resolution No. 910, ruled that any vessel that landed 15% with sea urchin of 6.5 cm UMLS of the total catch weight will be sanctioned. In this paper, a sampling design is presented to establish criteria regarding compliance with this provision. The plan provides a statistical methodology for the evaluation of the percentage of UMLS sea urchin, which corroborates and certifies the current legislation that sanctions and fines the capture of sea urchin that does not comply with UMLS values outlined in Regulation 44. Assuming a systematic sampling plan and under assumed UMLS values of 6.0, 6.5, and 7.0 cm, it is determined that 15% of total landings (margin of tolerance) of sea urchin under 6.5 cm is the optimal level. Thus, a correct specification of the UMLS allows protecting the most vulnerable fraction of the population from overexploitation for growth.

Short-term Estimate of Finfish Bycatch Discards in the Inshore Artisanal Shrimp Fishery of Guyana

The artisanal shrimp fishery in Guyana is important for livelihood and food security, involving around 300 vessels owned and crewed exclusively by Guyanese nationals. This fishery uses Chinese seines and operates in major river estuaries. It targets penaeid shrimp, but also retains some finfish and is known to discard a significant but undocumented quantity of smaller finfish bycatch. The lack of knowledge regarding the bycatch is a concern for fishery management and biodiversity conservation. In this study, we quantify for the first time the finfish bycatch discards through onboard observations (July—August 2016) of a single typical vessel operating in the Demerara estuary. Wet weights of the total catch, retained catch, and finfish discards were recorded separately for each of 76 seine hauls, and subsequently presented as catch rates per trip, catch rates per seine haul (kg/haul), and catch rates standardized per hour of seine net soak—time (kg/hr). A sub—sample of finfish discards was taken from every haul to determine taxonomic composition and species—specific length frequencies. Examination of 2,012 discarded finfish distributed among 32 species revealed high taxonomic diversity, none of which were considered vulnerable by the IUCN Red List. Most finfish discards were small (modal size class 5—7 cm fork length) and included juveniles of 15 species of importance to other fisheries in Guyana. On average, a standardized total catch rate of 14.8 kg was taken per hour of seine net soak—time, yielding 3.9 kg retained catch (shrimp and a few selected finfish), 10.3 kg of finfish bycatch discards, and 0.6 kg of miscellaneous invertebrate discards. This demonstrates significant wastage (finfish discards represent about 69% of the total catch weight) and potential for negative impact on biodiversity and other commercial fisheries. The information provided here addresses an important knowledge gap in the artisanal fisheries of Guyana.

Quantifying the behavioral and economic effects of regulatory change in a recreational cobia fishery

Fisheries economists typically assume recreational anglers make decisions that maximize individual angler utility, which may depend on fishery and regulatory conditions. Under this framework, changes in regulations can lead to target species substitution by anglers in response to shifts in expectations of trip utility. A stated preference survey was developed and distributed to recreational cobia (Rachycentron canadum) anglers in Virginia to explore the effects of regulatory change on angler decision-making, species targeting, and resulting economic outcomes. The survey included a series of hypothetical choice scenarios, where respondents were asked to select their most preferred alternative after being presented with different fishing trips targeting cobia, red drum (Sciaenops ocellatus), or summer flounder (Paralichthys dentatus). Seven regulatory treatments of the survey were distributed, providing anglers a variety of species targeting tradeoffs. A mixed logit model was used to estimate angler preferences associated with hypothetical trip attributes and regulatory environment. Changes in angler welfare resulting from changes in cobia regulations were then assessed. Anglers were found to prefer targeting cobia to red drum or summer flounder under status quo management. Increases in catch, average weight of catch, and legal harvest of cobia were also found to provide anglers greater improvements in trip utility compared to increases in these attributes for trips targeting red drum or summer flounder. The economic effects of regulatory change were asymmetric because restrictive regulations were found to reduce angler welfare whereas liberalizing regulations had no significant effects. Increased availability of alternative target species was found to dampen the negative welfare effects of restrictive cobia regulations due to predicted target species substitution by anglers.

Pengaruh Penggunaan Umpan dan Konstruksi Funnel terhadap Hasil Tangkapan Bubu Laut Dalam di Teluk Palabuhanratu

The main objective of this research was to analyze the influence of bait and funnel constructions on the catch of deep sea pot in Palabuhanratu Bay. The experimental fishing used each of 5 units rigid and soft funnel of the deep sea pots filled with bait of shark and ray meat. The result showed that shark and ray baits did not have a significant influence on the weight of pots catch. The rigid and soft funnel constructions also did not have a significant influence on the catch. Therefore, both shark and ray baits used on the deep sea pots for catching fish at the depth of 200 m in Palabuhanratu Bay had the same effectiveness. The rigid funnel pot was a more suitable construction to catch fish, because it was easy to construct, relatively heavy and fast to sink, so it reduced the setting time.

Prepared for change? An assessment of the current state of knowledge to support climate adaptation for Australian fisheries

Fisheries and marine ecosystems are challenged globally by climate change with subsequent biological and socio-ecological implications. Adaptation represents one pathway by which management agencies can seek to ensure sustainability of these resources for societal well-being, particularly when based on strong scientific evidence. Here, we examined the extent of primary scientific literature that is currently available to inform climate adaption initiatives for Australian fisheries. This is achieved via a systematic literature review for 99 harvested Australian marine species, aimed at identifying primary scientific articles that reported new knowledge of climate-driven biological changes and/or socio-ecological implications. We then assessed the quantity of scientific literature against estimated relative climate sensitivity scores for each species (from a previous study), and investigated factors that may influence relative research effort. We found that two-thirds of species had no peer-reviewed climate-related literature available, and that research effort among Australian fisheries species is most closely related to the number of commercial fish stocks per species, and commercial catch weight. We also found that the south-east and western Australian regions had the most climate-related biological information to support climate adaptation in fisheries management. Nonetheless, although accumulating knowledge of the biological and socio-ecological implications of climate change is important, increasing knowledge alone is insufficient to maintain the productivity and profitability of Australian fisheries in light of projected climate impacts. We suggest that the further use of this knowledge to inform decision-making processes is essential to ensure that climate adaptation options are fully explored, to allow sustainable and productive fisheries.

Analyses of the non-target catch from the Egyptian Mediterranean trawlers, off Port Said

The present study aimed to analyze the non-target catch in the Egyptian Mediterranean waters, off Port Said, during the period from spring 2017 to winter 2018. The analysis revealed that from 75 non-target species, fish constituted about 69.4% of the total catch weight, whereas invertebrates reached about 30.6%. For non-target fish, 51 fishes were identified (50 bony fishes and one elasmobranch), of which 17 lessepsian species were found. The high percentage of fish (82.67%) was with an average length between 4.0 and <9.0 cm. The highly represented fish species by numbers were: Engraulis encrasicolus (25.608%), Herklotsichthys punctatus (23.711%), Terapon puta (9.572%), Equulites klunzingeri (9.342%), Gobius niger (7.177%), Argyrosomus regius (6.280%), Alepes djedaba (4.155%), Gobius paganellus (3.397%), Sardinella aurita (2.525%), Ariosoma balearicum (1.093%) and Diplodus annularis (0.803%). Total analysis, seasonal analysis and an index of diversity (H′) for the non-target catch species were provided. On the other hand, length-weight relationship, condition factor and age composition were described for the most dominant species. For non-target invertebrates, 24 species were identified among which 13 lessepsian species were found. Shrimps and mantis shrimp Erugosquilla massavensis were the main constituents during the period of study. The authors propose to change the cod end mesh size from 2.5 cm to 4.0 cm to minimize the high percentage of non-target catch and preserve recruits of valuable species from over fishing along the Egyptian coast of the Mediterranean Sea while doing experiments to ensure the best results. Further, continuous monitoring and managements of trawlers must be put into consideration.

Further improvements in sorting grids for the crustacean trawl fishery off the Southern coast of Portugal

Bottom-trawl fishing for crustaceans off the Portuguese south and southwest coasts is a very important segment of the Portuguese fishing fleet, where annual rates of discarding have ranged from approximately 38% to as much as 70% of the total catch. Past experiments to address this problem encompassed the testing of different codend mesh sizes and configurations, square mesh windows and rigid grids to enhance species and size-selectivity. While the use of a Nordmøre grid has proved quite efficient in separating out blue whiting (Micromesistius poutassou), it also led to some losses of the two main crustacean target species, Norway lobster (Nephrops norvegicus) and rose shrimp (Parapenaeus longirostris). The present study addresses that limitation by using a modified grid with 20 mm bar spacing and two open sections, designed with the purpose of separating fish and crustacean species into upper and lower codends. Good separation was achieved, with about 80% of the blue whiting (in number) directed towards the upper trawl section and caught in the upper codend, while a similar percentage of Norway lobster was caught in the lower codend. The grid bars had 50% retention for Norway lobster at 34.1 mm carapace length. The results herein will enable this gear configuration to be fine-tuned with regard to codend mesh sizes and bar spacing, so as to optimize both retention of Norway lobster and exclusion of blue whiting. For example, compared to using the minimum 70 mm diamond mesh size, using an 80 mm diamond mesh upper codend would reduce Norway lobster catch weight by just 1.6% but reduce the number of blue whiting caught by 42%.

Analysis of opportunity loss of lift net operation in Makassar Water

Lift net was a Makassar traditional fishing gear that attached into the seabed, used paraffin lamps as fishing devices and used net with mesh size 0.5 cm. Lift net had low selectivity whereas in order to obtain sustainable fisheries, the catches should be mature fish phase (gonad ripe). This study aimed to determine the value of opportunity loss due to the low selectivity in operation of lift net. This research was held in June - July 2018 in Makassar Waters. This study used secondary data of South Sulawesi Fisheries Statistics 2010 - 2016, primary data such length and weight of lift net catches and some literature studies. There were five species caught by lift net such as mullet (Valamugil seheli), shrimp (Penaeus merguiensis), peperek (Leiognathus equulus), sardine (Sardinella gibbosa), and anchovy (Stolephorus commersonii). Based on the results, the percentage of mature fish of lift net catches was 60% of mullet, 20% of shrimp, 39% of peperek, 5% of sardine and 5% of anchovy. The average value of the opportunity loss of lift net operation during 2010-2016 in Makassar waters was Rp. 437,090,000.

Spatiotemporal bycatch analysis of the Atlantic halibut (Hippoglossus hippoglossus) longline fishery survey indicates hotspots for species of conservation concern

The Atlantic halibut (Hippoglossus hippoglossus) longline fishery is the second most valuable groundfish fishery in Atlantic Canada and received Marine Stewardship Council certification in 2013. The bottom longline fishery accounts for most halibut landings but incidentally catches nontargeted species (bycatch). Since 1998, Fisheries and Oceans Canada and the halibut fishing industry performed annual longline surveys across the Scotian Shelf and Southern Grand Banks stock management area to monitor halibut abundance, and at‐sea observers also recorded bycatch information. We examined the species composition and proportion of the survey bycatch and analyzed temporal and spatial trends in standardized weight of (a) halibut catch, (b) total bycatch, and (c) bycatch of species of conservation concern. From 1998 to 2016, 70% of the total catch by weight and 85% by number of individuals were bycatch. Over 100 identified species of finfish, sharks, skates, benthic invertebrates, marine mammals, and seabirds were caught as bycatch in the survey. This included four species listed under the Species at Risk Act (Northern wolffish, Anarhichas denticulatus; spotted wolffish, A. minor; Atlantic wolffish, A. lupus; Atlantic cod, Gadus morhua), and another 14 species awaiting a listing decision based on assessments by the Committee on the Status of Endangered Wildlife in Canada. Generally, the standardized weight of halibut and barndoor skate (Dipturus laevis) increased over time, while Atlantic cod, spiny dogfish (Squalus acanthias), white hake (Urophycis tenuis), and thorny skate (Amblyraja radiata) decreased. Spatial patterns indicated high bycatch levels on the southern Scotian Shelf and southern edge of the Southern Grand Banks, with hotspots for certain species of conservation concern. Our results identify temporal trends in threatened species and areas where they are susceptible to the Atlantic halibut longline fishery which can inform recovery strategies, bycatch levels and spatial zoning in fisheries management and marine conservation.

Effects of prolonging the trawl net summer fishing moratorium period in the East China Sea on the conservation of fishery resources

PDF HTML阅读 XML下载 导出引用 引用提醒 延长拖网伏季休渔期的渔业资源养护效应 DOI: 作者: 作者单位: 中国水产科学研究院东海水产研究所, 农业农村部东海渔业资源开发利用重点实验室, 上海 200090 作者简介: 严利平(1964-),男,研究员,研究方向为渔业资源评估和管理.E-mail:yanlp@ecsf.ac.cn 通讯作者: 中图分类号: S932 基金项目: 公益性行业（农业）科研专项经费项目（201303047）；农业部财政项目（2014-2018，2014-2017，2017-2018）. Effects of prolonging the trawl net summer fishing moratorium period in the East China Sea on the conservation of fishery resources Author: Affiliation: Key Laboratory of East China Sea Fishery Resources Exploitation and Utilization, Ministry of Agriculture and Rural Affairs;East China Sea Fisheries Research Institute, Chinese Academy of Fishery Sciences, Shanghai 200090, China Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:海洋伏季休渔制度是当前中国最主要的渔业资源管理制度之一，并在实践中得到不断调整与完善，新的海洋伏季休渔制度已于2017年发布实施。为论证新制度延长拖网休渔期的渔业资源养护效应，本研究依据2015—2017年每年5月东海区拖网大面定点调查资料，利用Ricker动态综合模型，从拖网的渔获结构特征和带鱼（Larimichthys polyactis），带鱼和小黄鱼的性成熟比例分别为92.04%~95.57%和13.82%~29.55%，幼鱼比例分别为74.94%~88.90%和0.03%~4.19%；带鱼种群经过4.5个月的休渔，其单位补充量资源量、单位补充量渔获量和平均渔获质量与3.5个月休渔期相比较，分别增加了7.04%、8.96%和20.78%。以上结果表明，提前并延长拖网休渔期，东、黄海主要经济渔业资源带鱼与小黄鱼的产卵群体和幼鱼得到进一步保护，资源增殖效果随着休渔期的不断延长而增加，新制度的休渔时间设置更趋合理。但由于开捕后的带鱼与小黄鱼渔获仍主要以当龄鱼为主，有必要同时配套执行现已颁布的最小网目尺寸和开捕标准等其他渔业资源管理措施，以确保伏季休渔制度主导下的渔业资源养护效果能真正得到巩固，渔业资源的种群结构能够得到切实好转与不断合理化。 Abstract:The summer fishing moratorium system, the main fishing management system in China, has been continuously adjusted and perfected in practice. In order to evaluate the conservation effects of prolonging the trawl net summer fishing moratorium period, which is contained in the new summer fishing moratorium system and promulgated in 2017, on the fishery resources, the data from the bottom trawl surveys in May during 2015-2017 and the dynamic integrated Ricker model were used to quantitatively analyze the structural characteristics of trawl catches and the dynamics of fish species such as the hairtail (). The results showed that the hairtail and the small yellow croaker () were the main organisms that were trawled in May, and their sex maturity ratios were 92.04%-95.57% and 13.82%-29.55%, respectively, while the proportion of juvenile fish for the two species were 74.94%-88.90% and 0.03%-4.19%, respectively. Compared with that from the previous 3.5 month fishing moratorium period, the biomass per recruit, yield per recruit, and the average catch weight of hairtail increased 7.04%, 8.96%, and 20.78%, respectively, after the newly enforced 4.5 month fishing moratorium period. According to our study, advancing and prolonging the trawl net moratorium period could further protect the spawning groups and juveniles of the hairtail and the small yellow croaker, which were the main economic fishery resources in the East China Sea and the Yellow Sea. The resource enhancement effect was more significant with the longer moratorium period, so the time setting of the new summer fishing moratorium system was reasonable. However, after the newly enforced summer fishing moratorium period, the main hairtail and little yellow croaker catch were still dominated by 1-year-old fish. Thus, it is necessary to support the implementation of other fishery resource management measures in addition to the new summer fishing moratorium system, such as the minimum mesh size and the open capture standard, to ensure that the conservation effects are firmly established and that the population structure of the fishery resources can continuously improve. 参考文献 相似文献 引证文献

Bycatch composition of cutlassfish trawlers during fishing season in Bushehr and Hormozgan, Persian Gulf, Iran

Fouladi Sabet A, Paighambari SY, Pouladi M, Raeisi H, Abbaspour Naderi R. 2018. Bycatch composition of cutlassfish trawlers during fishing season in Bushehr and Hormozgan, Persian Gulf, Iran. Biodiversitas 19: 2275-2282. This investigation was conducted to determine the bycatch composition of cutlassfish (Trichiurus lepturus) trawlers in Bushehr and Hormozgan waters during fishing season 2013. Data collection was carried out in the summer for Bushehr and in the autumn for Hormozgan province for one month. All trawler vessels were equipped with a 36 m head rope and 75 mm stretched mesh size in the codend and 90 to 200 mm stretched mesh size in the panel. 47 species included 35 species of teleosts, 9 species of elasmobranches and 3 species of invertebrates were identified in Bushehr. Also, 48 species included 38 species of teleosts, 7 species of elasmobranches and 3 species of invertebrates were identified in Hormozgan. The weight and numerical averages of bycatch species were 25.41 (kg h-1) and 205.9 (n h-1) in Bushehr, and 92.58 (kg h-1) and 440.4 (n h-1) in Hormozagan. I. megaloptera, S. tumbil, N. japonicus, D. acuta, C. sexfasciatus, L. equulus in Bushehr and P. sextarius, I. megalopteran, M. cinereus, P. macrophthalmus, N. japonicus and S. tumbil in Hormozgan had highest catch weight. Based on the weight and number, PCA and nMDS methods were indicative of two different assemblages in hunting places. Furthermore, ANOSIM similarity analysis confirmed the results of PCA and nMDS and showed a significant difference in the catch composition of two fishing zones.

Prediction of delayed mortality using vitality scores and reflexes, as well as catch, processing, and post-release conditions: evidence from discarded flatfish in the Western Baltic trawl fishery

Abstract The EU discard ban and its high-survival exemption exposed our lack of scientific evidence on discard survival in the fisheries. Discard survival is known to be highly variable and influenced by numerous factors, including conditions during the catch, on-board the fishing vessels, and post-discard. Therefore, obtaining unambiguous results in discard survival experiments is challenging. We conducted the first systematic year-round discard survival study of flatfish in the Western Baltic Sea on-board a commercial stern trawler under realistic fishing conditions (13 monthly hauls from May 2015 to May 2016) to test whether delayed mortality can be predicted by vitality scores and reflex action mortality predictor (RAMP) scores in combination with variable conditions during catch, processing, and post-release. The factors vessel type, gear, haul duration, fishing ground, depth, handling time, and processing procedures were kept constant as much as possible. On-board, live individual flatfish were tested for vitality and the presence of reflexes for RAMP, then “discarded” and kept in cages on the bottom of the seafloor for about a week after which the delayed mortality was determined. The proportions of “discarded” plaice, flounder, and dab that were dead after being kept in the cages ranged from 5% to 100%, 0% to 96%, and 33% to 100%, respectively. Higher mortalities occurred in summer-autumn when air and water temperatures were higher, catches smaller, and catches contained smaller proportions of roundfish. Relationships between RAMP scores and mortality probabilities varied substantially across the monthly trials. Indeed, in addition to RAMP or vitality scores and individual reflexes, the factors air and water temperature and catch weight and catch composition were significant in logistic GLMs explaining delayed mortality. Cross-validations indicated that delayed mortality could be predicted by these models with a reasonable accuracy. Nevertheless, the presence of possible confounding effects calls for caution in inferring causality and extrapolating the conclusions on predictability.

The “discard problem” in Mediterranean fisheries, in the face of the European Union landing obligation: the case of bottom trawl fishery and implications for management

Since the first introduction of the landing obligation (a.k.a. Discard ban) in 2015, the EU Mediterranean fisheries are facing some unforeseen challenges. The demersal bottom trawl fisheries, being the most significant contributors to the so-called 'discard problem', are confronted with the greatest challenges. Data from the Italian and the Greek fleet, spanning over two decades (1995–2015), were analysed with the intention of revealing the diversity and heterogeneity of the discard problem, especially for regulated species. Species composition of discards, as well as discarding rates, were shown to be irregular, fluctuating among areas, depth strata, seasons and years. Although fish dominated the discarded gross catch in weight, benthic invertebrates (other than commercial cephalopods and crustaceans) were the taxa discarded almost exclusively. The established minimum conservation reference size was largely ignored by fishers. From a management point of view, the present investigation suggests that the recently established Discard Management Plans lack scientific evidence (given the high intrinsic variability of the parameters and confusion regarding the rules) and provide exemptions from the landing obligation that will in practice allow the average Mediterranean bottom trawl vessel to continue business as usual. Moreover, detecting if these rules are actually respected is an almost impossible task for the Mediterranean control and enforcement authorities. Incentivizing the adoption of fishing technologies and practices that reduce pre-harvest mortality and post-harvest discards, while avoiding damage to sensitive marine species and habitats, seems the only way to move forward, rather than dealing with the problem after it has occurred.

Alternatives for reducing the environmental impact of an ammonia production plant adjacent to a coastal lagoon in the southeastern Gulf of California

There is an increasing demand for N-fertilizers and the manufacture of N-products worldwide. In Mexico, ammonia production is being promoted by the government, but this development is associated with several environmental impacts. This study examines the causes, effects and mitigation alternatives related to the installation and operation of an ammonia production plant adjacent to a coastal lagoon. A multiplicity of causes (and effects) was identified: water suction (elimination of plankton and larvae), effluent discharge (thermal contamination, salinization, and the effects of chlorine), and the conversion of wetlands (loss of habitat and nursery areas, biodiversity, fishery benefits, retention of contaminants, coastal stabilization, carbon storage and aesthetic value). At present, it is estimated that wetlands (9146 ha mangroves + 22,641 ha others) in the Ohuira-Topolobampo lagoon sustain the production of 3000 t live weight of seafood catches per year, implying that the conversion of 126 ha of wetlands could represent for fishermen a catch reduction of 11.9–41.3 t of shellfish per year and a decrease in the annual retention load of up 0.52 kg Cd, 41.0 kg Cu, 0.40 kg Hg, 280 kg Pb, 88.2 t P and 75.6 t N by wetland sediments. To mitigate the environmental effects associated with the installation and operation of the plant, the following is recommended: (i) afforestation of an equivalent area (126 ha), (ii) installation of an exclusion system for fauna to avoid the incidental capture of plankton and larvae, (iii) the use of cooling towers, and (iv) the selection of an appropriate discharge point for the effluent. A list of fauna and flora of the lagoon, as well as environmental services that could be compromised and affected by the operation of the ammonia production plant, is presented. This study is the first to analyze and document such effects and mitigation options related to land conversion and water management, providing useful information for decision makers.

Laju Tangkap dan Hasil Tangkapan Bagan Apung pada Jarak Penempatan Berbeda di Perairan Teluk Palabuhanratu, Sukabumi, Indonesia

The waters of Palabuhanratu Bay known as the main fishery base in Southern Java Indonesia because dynamical of oceanography influenced by the Indian Ocean. The common fishing gear used in these waters is the lift net, utilizing the phototactic properties of the fish. To determine the catch rate of lift net, focus of this study is to assess the catches with two different fishing areas of lift net with the coordinates of 07° 00' 00.6 S and 106° 32' 12.1 E (near from coast); 06° 59' 57.7 S and 106° 31' 39.7 E (far from coast). Catch rate analysis used Shindo's formulation interpretation, with the required data being the catch and effort. Captures near and far are dominated by Hairtail Fish weighing 3,3 - 38,5 kg with average catch weight for each trips ranging from 12,1 - 12,8 kg. The catch rate patterns for each type of fish did not differ significantly, the maximum value is Hairtail Fish on the far lift net and the minimum value is Mysis in the near lift net, and both lift nets have the same catch rate for the Squid and Seed Mackerel species. The main catch rate for the near lift net is 0,09 kg/h and for the 0,19 kg/h far lift net, while the side catch rate for the lift net is 2,21 kg/h and the chart is 2,45 kg/h.

The prevalence and potential fisheries consequences of Heterosporis sutherlandae in a Minnesota lake.

Heterosporis sutherlandae is an emerging microsporidian fish parasite in the Great Lakes region. H. sutherlandae forms lesions in the muscle tissue of fishes important to aquaculture and sport fishing. These lesions render the filet inedible and may have fitness consequences. We evaluated the prevalence and severity of H. sutherlandae among yellow perch (Perca flavescens) in a known-positive Minnesota lake, and used an equilibrium yield model to evaluate impacts on harvest. Twenty-eight percent of the 400 yellow perch sampled were infected with H. sutherlandae. Males were 1.5 times more likely to be infected than females and were more severely infected. The presence of the parasite did not vary with relative weight or age, but infection severity was highest among older individuals that were in better condition. These results suggest that males are more susceptible to infection, and that infection is not associated with maturity or a gape-limiting food source. These results also suggest that heterosporosis increases in severity with time or by increased exposure. Our equilibrium yield model found that a 10% increase in mortality due to H. sutherlandae could result in 30% and 10% reductions in yield and mean catch weight, respectively. The results of this study direct future field sampling and laboratory experiments to further understand and predict the impacts of this parasite.

Assessment of fishing gear and catch rate in Oguta Lake, south Eastern Nigeria

This study was carried out in Oguta Lake, Imo State, Nigeria, from January, 2012 to December, 2013 at five stations (Onu Utu, Okposha, Ogbe Hausa, Osemotor and Ede Ngwugwu) to ascertain the percentage abundance and catch rate of gear and craft. The average weight of fish caught per canoe per day ranged between 3.2 kg for Basket and Drum traps to 47.1 kg for boat seine net. The gill nets ranged between 6.0 to 13.0kg per canoe per day with mean weight of 8.60±2.91kg, the cast net had values ranging from 1.0 to 7.0 kg with a mean weight of 4.3±2.49 kg. Lift net yielded an average of 3.4 kg per canoe per day. Gill nets were the main gear used by fishers, followed by long lines and cast nets at the lake. It is important to locate all the fishers operating in the lake and daily record of catches be collected for a more accurate picture of the total catch and fish species. Mesh size regulation prevent over exploitation of young fish, before they attain sexual maturity. It is recommended that the cost of procuring fishing inputs such as fishing gear and crafts and safety kits should be monitored by government and be subsidized for the fishers.Key words: drum trap, crafts, catch, exploitation, Oguta, mesh size, trap

Management of deep-water sharks’ by-catch in the Portuguese anglerfish fishery: from EU regulations to practice

The European Union banned fishing operations with trammel, entangling and gillnets in Portuguese continental waters at depths >200m in consideration of the potential impact of fisheries on deep-sea sharks. Derogation could be considered if Member States demonstrate that by-catch mortality does not adversely affect this group of species. This regulation has had an impact on the trammel net fishery for anglerfish (Lophius piscatorius and Lophius budegassa), one of the most important Portuguese multi-species fisheries. This study evaluates the impact of this fishery on deep-water shark populations by looking at onboard observations of by-catch in the commercial fishery and by analysing survey catch composition. Results suggest that this fishery has a very low impact on deep-water shark populations: by-catch was <5% by weight of the total catch in 98% of the hauls conducted in the depth range allowed for this fishery (<600m). Frequency of occurrence of deep-water sharks was also low. Etmopterus spinax and Etmopterus pusillus were the only species found to overlap with this fishery to any great extent; all the others largely distribute at depths greater than 600m. A higher overlap is expected in hauls catching L. piscatorius, which seems to distribute at greater depths, but more information is needed to clarify the distribution pattern of this species. Scientific data supports the proposed change to the EU regulation. If necessary, future management measures may rely on spatial closures, but would require enhanced knowledge on species’ spatial distributions and also on social and economic aspects of this fishery.

Forecasting the ongoing invasion of Lagocephalus sceleratus in the Mediterranean Sea

Invasive species from the Suez Canal, also named “Lessepsian species”, often have an ecological and financial impact on marine life, fisheries, human well-being and health in the Mediterranean Sea. Among these, the silver-cheeked toad-fish Lagocephalus sceleratus (Gmelin, 1789) has rapidly colonised the eastern Mediterranean basin and is currently moving westwards. This pufferfish has a highly opportunistic behaviour, it attacks fish captured in nets and lines and seriously damages fishing gears and catch. It is a highly-toxic species with no immediate economic value for the Mediterranean market, although it currently represents 4% of the weight of the total artisanal catches. Consequently, the possible effects on Mediterranean fisheries and health require to enhance our understanding about the future geographical distribution of this pufferfish in the whole basin.In this paper, an overall habitat suitability map and an effective geographical spread map for L. sceleratus at Mediterranean scale are produced by using cloud computing-based algorithms to merge seven machine learning approaches. Further, the potential impact of the species is estimated for several Mediterranean Sea subdivisions: The major fishing areas of the Food and Agriculture Organization of the United Nations, the Economic Exclusive Zones, and the subdivisions of the General Fisheries Commission for the Mediterranean Sea. Our results suggest that without an intervention, L. sceleratus will continue its rapid spread and will likely have a high impact on fisheries. The presented method is generic and can be applied to other invasive species. It is based on an Open Science approach and all processes are freely available as Web services.

Influence of tow duration on catch performance of trawl survey in the Mediterranean Sea

The aim of this study was to assess the effect of tow duration on catch per unit of swept area (CPUE), trawl catch performance, and the proportion of the species caught in a trawl survey. Longer tows are expected to have a greater probability of catching species. An average of 26 species were caught in the first 30 minutes, whereas only about one additional species was caught in the next 30 minutes in longer tows. The shorter tows involved a decrement in catch weight for 11 of the 12 target species sampled, demonstrating that tow duration did affect catch per unit of swept area CPUE. The shorter tows were associated with a significant reduction of the overall CPUE in terms of weight of the main target species and of the total catch (circa 60%). The same strong reduction of around 70% was found in particular for European hake (Merluccius merluccius) and surmullet (Mullus spp) and 50% for Nephrops (Nephrops norvegicus). The shorter tows were less efficient in catching large-sized hake, surmullet, Nephrops, Atlantic horse mackerel (Trachurus trachurus), and poor cod (Trisopterus minutus), even though the difference was significant only for Nephrops. Regardless of the p-value statistic, these findings suggest that the continuity of survey time series would be severely impaired by changing tow duration. Further work is required to explore a way to reduce tow duration without reducing CPUE.