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.

Analysis of Crayfish Catches Using Bubu Wau in Laut Tawar Lake, Central Aceh, Aceh

Laut Tawar Lake is located in the town of Takengon, Central Aceh district. Currently, Laut Tawar Lake has been utilized by the surrounding community as a fishing spot. One of the fishing gears used by fishermen is Bubu wau. One of the catches obtained by fishermen is crayfish. The crayfish has a high economic value, so the lack of control over the intensity of the catch also causes the average size of the crayfish caught, because catching crayfish is a transition from catching Rasbora tawarensis. One of the problems that frequently occur and research on crayfish has never been done before. Therefore, this research needs to be done. The purpose of this study was to determine fishing catch compositions of Bubu wau and the size distribution of crayfish carapace length of Bubu Wau fishermen in the Teluk One-one, Laut Tawar Lake. The research was carried out in about March 2021. The description of the fishing catch composition was analyzed by using the describded method. The size distribution of crayfish carapace length was analyzed by the Sturgess rule. From the results of the study, it can be concluded that the catch compositions of Bubu wau in Teluk One-one are crayfish, suckermouth catfish, channeled apple snail and tilapia. The type of crayfish caught by fishermen’s Bubu wau was Cherax quadricarinatus amount of 4232 individuals (89% of the total catch), where the total length of the dominant crayfish carapace was 4.4-4.9 cm with a total number of 1403 and the least with a size of 8.6-9.1 cm was 1 crayfish from the total catch

The bottom gillnet catch composition in Sasak Ranah Pasisie coastal water, Pasaman Barat regency

This research aimed to determine the catch composition of the bottom gillnet at Sasak Ranah Pasisie coastal water, Pasaman Barat Regency, West Sumatera. The research was conducted from January to February 2019 with total of 15 fishing trip using the bottom gillnet. The gillnet used 100 m of length, 3 m of width, and 2 inches of mesh size. Each of fish sample was identified, counted, measured their length and weight, and determined the way of fish captured by gillnets. The result showed that fish catches composition using bottom gillnet consist of 26 species, i.e., 22 species of fish, two species of crabs, and two species of shrimps. The highest catch was Common ponyfish (Leiognathus sp.) as much as 23%. The other captured species were Silver grunt (Pomadasys sp.) 20,2%; Leaftail croaker (Otolithes sp.) 14,5%; Largehead hairtail (Trichiurus sp.) 6%; Moustached thryssa (Thryssa sp.) 5%; and Black pomfret (Parastromateus sp.) 5%. Based on the way of fish captured on the bottom gillnet, the predominantly fish were wedged as much as 39% from the total of fish catches, followed by gilled (30%), entangled (26%), and snagged (6%).

The effect of escape gap on the cube folding trap on fish catches composition and trap rate at the northern coast of Tuban regency

This study aims to determine the effect of escape gap on catch composition, CPUE, and trap rate at the northern coast of Tuban Regency. The research was conducted by ten trips of experimental fishing at different locations in November 2019. A total of 60 units of cube folding traps were installed long line, consisting of cube folding traps without escape gaps, cube folding traps with escape gaps 6x3 cm, cube folding traps escape gaps 7x4 cm, 20 units, respectively. The fish catch composition consists of 18 species of 6 groups, i.e., fish, swimmer crab, shrimp, hermit crab, and snail. Fish were the most dominant group captured by cube folding traps in the northern coast of Tuban Regency (59.7%), followed by swimmer crab, snail, crab, shrimp, and hermit crab. The highest catch per unit effort was found in cube folding traps with escape gaps 7x4 cm as much as 6,94 gr/traps/trip. The highest of the trap rate (18%) was obtained in the cube folding traps without escape gap. There was a significant difference (p=95%) in the weight of fish catches and CPUE between cube folding traps without escape gaps and the cube folding traps with escape gaps 7 x 4 cm.

Spatiotemporal Variation in the Catch Composition and Abundance of Precious Corals Around Taiwan: Implications for Fisheries Management

Precious corals are a fishery resource of cultural and religious importance. Because of their high commercial value, precious corals have been exploited for several centuries in the Mediterranean and for almost one century in the Northwest Pacific. Taiwanese fishing fleets have harvested precious corals since the 1920s; however, management regulations have only been promulgated since January 2009, when the catch and effort data of fisheries began to be collected. This study examined spatiotemporal variation in the catch composition and abundance of precious corals Corallium, Hemicorallium, and Pleurocorallium spp. around Taiwan using fishery data from 2009 to 2018 and discussed its implications for fisheries management. Licenses are issued for 60 vessels annually, and the annual total catch was 2.9–3.5 t between 2009 and 2018, peaking in 2015 and then decreasing sharply in 2016. Because of the use of non-selective fishing gear, dead and fossilized colonies were included in the total catches of the fishery. Fossilized colonies were predominant (average 78.5%) in the total catches, whereas the proportion of live colony catches accounted for less than 5%. Pink coral (Momo) was predominant in the total and live colony catches during the 10-year period. The Taiwanese precious coral fishing fleets are restricted to harvesting precious corals in five designated fishing grounds (DFGs; A–E). The fishing effort (vessel⋅day) was mainly concentrated in DFG-A (average 56.6%), which accounted for an average of 63.9% of the total catches. However, the live colony catches were largest in DFG-E (average 39.9%) and DFG-A (average 39.6%). The annual catch rates of live colonies decreased in two major fishing grounds (DFGs-A and DFG-B), whereas it increased in two minor fishing grounds (DFGs-C and DFG-D). The temporal variation in occurrence rates of live colonies decreased between 2015 and 2018, indicating a declining trend for precious coral populations around Taiwan. These results indicate that an unsustainable condition may occur in the near future if the precious corals continue to be harvested at the current scale. Revised regulations for the Taiwanese precious coral fishery should contain proposals on fishing gear modifications, a rotational harvesting scheme, or both; such measures can contribute to the conservation of precious coral populations. Regional cooperation in fisheries management is necessary to achieve the sustainable development of precious corals and their fisheries in the Northwest Pacific.

Catch Composition of Set Net Fisheries during Normal Season in Sungai Sembilang Waters, Selangor, Malaysia

Highlight ResearchThe Set Net was identified and recorded.Length and weight of the catch of set net was analyzed. AbstractSet net fisheries are made according to traditional fishing gears method in the coastal waters of Sungai Sembilang, Selangor, Peninsular Malaysia. These fisheries system are the passive structure of gear used to catch fish that swim in shallow water with muddy substrate. This study focused on determining the species variety and the possible future of set net fisheries in Sungai Sembilang. Catch composition of set net was investigated based on the catch data during July to December 2020 and continued from January to February 2021. The catch data was recorded by a research assistant on site during fishing season. The data consist of species, length and weight of all catches recorded. Total catch of 60 fish species belonging to 23 families were captured during this study period. Ariidae (31.73%), Clupeidae (11.56%), and Scatophagidae (7.96%) were determined as dominant families caught this set net. The total dominant catch amount of species Plicofollis argyropleuron (18.71%), Nemapteryx caelata (9.96%), and Anodontostoma chacunda (8.92%) compromised 37.6% of the total catch. This type of fishing gear can be used by local fisherman to catch fishes and can prevent trawl net from come closer to the shore. This study would provide some general useful information about the status of set net fisheries as well as the species abundance caught from the set net.

Landing and distribution of captured fish in selected landing centers in Kishoreganj haor, Bangladesh

The present study illustrates species diversity, landing quality and catch composition of fish in 10 fish landing centers of 5 haor upazilas of Kishoreganj haor for 12 months from January 2018 to December 2018. A total of 15 different types of fishing gears were detected to harvest fish in different stations throughout a year. Most of the fishing (46.88%) was conducted by small groups of 2 – 5 fishers, while 24.87% of the fishing was conducted by 6 – 10 fishers. The average depth of water in haor associated rivers and inundated lands during monsoon period varied from 4.87±0.99 to 15.2±6.71 and 2.6±0.55 to 6.2±2.68 feet respectively. Fifty different types of fish species were landed in the selected 10 landing centers, where both cultured fish and captured fish were present. Fishes under the Cyprinidae family included 9 species, viz. Labeo rohita. Gebelion catla, Cirrhinus cirrhosus, Labeo calbasu, Hypophthalmichthys nobilis, Hypophthalmichthys molitrix, Cyprinus carpio, Ctenopharyngodon idella, Labeo gonius covered a maximum of 12450.61±468.32 MT. The second largest landed fish under the family Schilbeidae included 4 species Silonia silondia, Mystus armatus, Mystus cavasius Pseudeutropius atherinoides. Other fish species landed were identified as: 4 species under the family Mastacembelidae, 2 species under Siluridae, 3 species under Clupidae, 1 species under Ambassidae, 2 species under Palaemonidae, 3 species under Channidae, 1 species under Gobidae, 2 species under Bagridae and 1 species from each of the family Heteropneustidae, Pangasiidae, Clariidae, Ailiidae, Botiidae, Nandidae, Cichlidae, Anabantidae, Osphronemidae, Ambassidae, Notopteridae, Notopteridae,Belonidae and Gobiidae. Highest number 14 species landed were under catfish category, followed by 9 species of major carp. The captured total fish landed in 10 landing centers in 12 month period accounted 12,574±1029.64 MT, but the cumulative total landed fish, including pond fish, was 15,795±1666061.93 MT, as calculated by 45 Aratdars of 10 landing centers. About 88.35% fishermen sold the captured fish at local arat, but the rest (11.65%) were sold to large traders (paiker), retailers and consumers. A 56.6% of the fishermen cleaned the captured fish by river water, while 43.4% fishermen did not use water for washing fish before selling. After harvest, 45.62% fishers used clean utensils for carrying fish to arat and 54.38% used uncleaned utensils. Average harvest per fishermen per day was 23.9 kg, of which 22.26 kg was sold in the market and 1.64 kg was used for own family consumption. Out of total fish landed, a 45.2% was transported by fish hold of the country boat, 21.9% by bamboo basket and 14.8% by plastic crate. Relatively small quantity of fish was transported by insulated ice box (4.7%), aluminum container (2.7%) and gunny bag (3.2%). A 32.6% fisherman used ice and 67.4 % fishermen did not use ice after harvesting of fish. During fishing season, fish and ice ratio used by the transporters was 2.62:1. The highest number of auctioneers were found in Chamra Ghat of Karimganj, while lowest were in Nikli, with an area of 55±1.44 and 25±8.42 decimal area per auctioneers being used for fish business. Asian Australas. J. Biosci. Biotechnol. 2021, 6 (2), 75-88

Impact of a ring net fishery in the inshore marine waters of Kilifi on the reproductive biology of six pelagic fish species

Ring nets are modified purse seines used for pelagic fishing along the Kenya coast. This method is however associated with potential negative environmental implications in inshore and shallow fishing grounds. Biological impacts on selected pelagic species caught in the marine waters of Kilifi were investigated during the Southeast Monsoon season (SEM) in April, May and September 2014, and the Northeast Monsoon season (NEM) in October and November 2014, and March 2015. Amblygaster sirm, Rastrelliger brachysoma, Sardinella gibbosa, Rastrelliger kanagurta, Hemiramphus far and Sphyraena obtusata were the most abundant species caught by the ring nets and comprised 68.9 % of fish catch composition. Analysis of ring net impacts on the fish sizes and maturity status were conducted for the NEM and SEM seasons. The catch composition for A. sirm in October comprised of 53.3 % juveniles and 53.4 % juveniles for S. obtusata in November. High percentages of H. far (78.3%) and S. obtusata (58.9 %) were captured in September. Incidences of undersize fish for A. sirm, S. gibbosa, R. kanagurta and R. brachysoma were observed across the seasons. Sex ratios for A. sirm, R. brachysoma, R. kanagurta and S. obtusata in the NEM season deviated from a normal ratio of 1:1 with more males observed. Females were dominant in the catch for H. far (1: 1.28) but the ratio was not different for S. gibbosa (χ² = 5.564, df = 1, p = 0.21). Males were dominant for A. sirm (1: 0.8) and S. gibbosa (1: 0.7) in the SEM season but the ratios were not different for H. far, S. obtusata, R. brachysoma and R. kanagurta. Differences in sex ratios were attributed to fish migrations and reproductive processes. Ring nets fished relatively offshore during the NEM season and targeted mainly spawning aggregations in stage IV. Immature fish in stage I and II which comprised of juveniles were harvested within sheltered inshore waters in the SEM season. Use of ring nets to target juveniles and spawning aggregations may disrupt recruitment processes. To enhance sustainable management of the ring net fishery, there is a need to develop harvesting strategies based on the information on stock status of the target fish.