Number Of Individual Fish Research Articles

Composition of gillnet catches based on network size at UPT Fishery Port of Riau Province

Gill net catches are one of fishermen's dominant fishing gear at UPT Dumai City Fishing Port. Gill net catches are easy to operate, have a low price, and are durable. This research was conducted in July-August at UPT Port of Fisheries, Riau Province. This study aimed to determine differences in gill net catches based on different mesh sizes. The method used is the survey method. The catch of gill nets by type with a mesh size of 2 inches is 25 fish species. Based on the weight and number of individual fish, it was dominated by lomek (Harpodon sp), namely 1,359.5 kg or 21.5% and 16,314 individuals or 27.18%. The catch in the 3-inch mesh size was 23 species of fish. The percentage of catches based on weight dominated by senangin (Eleutheronema tetradactylum) was 30.38% (1,353.5 kg), and based on the number of individuals dominated by pomfret of 18.72% (4,534 individuals). The main catches in gill nets at UPT Dumai are lomek (Harpodon sp), senangin (Polynemus sp), pomfret (Bramidae sp) and machete (Chirocentrus sp). The primary and bycatch yields for the 2-inch mesh were 51.58% and 42.42%, while the 3-inch mesh sizes were 57.99% and 42.01%.

UKURAN KEPADATAN DAN POTENSI IKAN BARONANG TOMPEL (Siganus guttatus Bloch 1787) DI TELUK KOTANIA SERAM BAGIAN BARAT

Spotted rabbitfish (Siganus guttatus Bloch 1787) are valuable commercial fish species. Research on the fish species has been carried out in the waters of Kotania Bay, aiming to obtain information about size, density and potential of the fish species. Data are collected about total length (TL), weight and number of individual fish at four observation stations using 120m length of bottom gillnet with mesh size of 2.0, 2.5, 3.0 dan 3.5 inches. The bottom gillnet is operated in a circle that starting two hours before the low tide then the spotted rabbitfish caught are collected at the low tide. The results showed that the total length of the spotted rabbitfish is in the range of 11,3 – 33,9 cm which has dominated by fish with sizes of 18, 24 and 26 cm. Mean density of the fish is 209 individual/ha, so the abundance the fish in the area of seagrass beds 823.62 ha was estimated as 172.486 of fish individual, it’s 72,51% or 125.070 individuals are those fishes that has spawned for the first time. The mean weight of the spotted rabbitfish at this size is 533,51 grams, so calculated biomass is 66,73 tons and MSY value is 33,365 tons in wet season.

Marine Resource Recovery Following the COVID-19 Event in Southern Thailand

This study investigated coral and reef fish recovery following the COVID-19 event between low and high environmental disturbance reefs at Racha Yai Island, Southern Thailand. Three and four 50-m permanent line transects were set at low and high environmental reefs to collect the percent of live coral cover, fish diversity and abundance, and fish trophic-functional groups based on diet and habitat use. Our results showed a significant rise in the percentage of live coral cover, the number of individual fish, the number of fish species, and species richness at both bays following the COVID-19 lockdown due to a crucial reduction in human activities on the reef. In addition, there were increases in the number of corallivore fishes belonging to Chaetodontidae and Pomacentridae families and a reduction of omnivorous fish at the fish-feeding tourist attraction reefs due during the COVID-19 lockdown due to reducing fish-feeding tourism. This indicated that restricted human activities and reduced anthropogenic stress on a coral reef may have substantial short-term impacts on reef fish diversity. Our insights could help designate guidelines to manage tourist impacts on coral reefs and aid in their prolonged persistence. Doi: 10.28991/CEJ-2022-08-11-011 Full Text: PDF

Struktur Komunitas Ikan di Pantai Karang Jahe Rembang

Fish play an important role both ecologically and economically. Fish also play a role in the food chain cycle, can be used as food and tourism commodities. This study aims to examine the structure of the fish community, to analyze the relationship between the number of individual fish and the physical and chemical parameters of the waters and to determine the ecotourism potential of fish diversity in Karang Jahe Beach, Rembang. The research was conducted at 5 different stations, namely tourist area, pond area, river flow, around mangroves, and marine area close to coral reef communities. Fish were caught using fishing nets and fishing trawler. Sampling at each station was repeated 3 times. The results obtained 22 species of fish belonging to 16 families, namely Epinephelus fuscoguttatus, Lutjanus bitaeniatus, Lutjanus ehrenbergii, Chanos chanos, Liza alata, Mugil sp, Oreochromis mossambicus, Pseudapocryptes elongatus, Periophthalmus sp., Eubleekeria jonesi, Eubleekeria elongate, Eubleekeria elongate Sardinella lemuru, Pennahia argentata, Trichiurus lepturus, Scomberomorus commerson, Stolephorus sp, Stolephorus indicus, Stolephorus commersoni, Chromis analyst, Terapon theraps and Lagocephalus inermis. The species diversity index is classified as low and moderate. The species evenness index is classified as low, medium and high. The dominance index is classified as low and high. Physicochemical parameters of Karang Jahe Beach waters such as temperature, pH, salinity, DO, turbidity and TDS are still classified as suitable for life, while the brightness parameter does not support fish life.

In Situ Measurement of Sound Attenuation by Fish Schools (Japanese Horse Mackerel, Trachurus japonicus) at Mid-Frequency Bands

Acoustic waves are attenuated by fish schools as they propagate through the ocean. The attenuation by fish schools is not currently considered in fishery acoustics and sonar applications, especially at mid-frequency bands. In this study, fish school attenuation experiments were conducted with a number of individual fish in situ in a net cage at mid-frequency bands (3–7 kHz). The target fish species was the Japanese horse mackerel (Trachurus japonicus), which typically forms fish schools in the coastal ocean of northeastern Asia. The attenuated acoustic waves were measured for the cases of non-net, only net (0), 100, 200, 300, 400, and 500 individual horse mackerels in the net cage. Results showed that the acoustic signal attenuation increased with the number of horse mackerels. The mean and maximum attenuation coefficients were approximately 6.0–15.4 dB/m and 6.5–21.8 dB/m for all frequencies, respectively. The measured attenuation coefficients were compared with the ones from previous studies to propose new regression models with normalized extinction cross-sections of weight and length of fish. This study confirmed that the fish school attenuation could not be ignored and compensated at mid-frequencies in the ocean. These results would be useful for fishery acoustics, especially in the development of scientific echo-sounder, and naval applications of sonar operations and analysis.

Marine biodiversity at the end of the world: Cape Horn and Diego Ramírez islands.

The vast and complex coast of the Magellan Region of extreme southern Chile possesses a diversity of habitats including fjords, deep channels, and extensive kelp forests, with a unique mix of temperate and sub-Antarctic species. The Cape Horn and Diego Ramírez archipelagos are the most southerly locations in the Americas, with the southernmost kelp forests, and some of the least explored places on earth. The giant kelp Macrocystis pyrifera plays a key role in structuring the ecological communities of the entire region, with the large brown seaweed Lessonia spp. forming dense understories. Kelp densities were highest around Cape Horn, followed by Diego Ramírez, and lowest within the fjord region of Francisco Coloane Marine Park (mean canopy densities of 2.51 kg m-2, 2.29 kg m-2, and 2.14 kg m-2, respectively). There were clear differences in marine communities among these sub-regions, with the lowest diversity in the fjords. We observed 18 species of nearshore fishes, with average species richness nearly 50% higher at Diego Ramírez compared with Cape Horn and Francisco Coloane. The number of individual fishes was nearly 10 times higher at Diego Ramírez and 4 times higher at Cape Horn compared with the fjords. Dropcam surveys of mesophotic depths (53–105 m) identified 30 taxa from 25 families, 15 classes, and 7 phyla. While much of these deeper habitats consisted of soft sediment and cobble, in rocky habitats, echinoderms, mollusks, bryozoans, and sponges were common. The southern hagfish (Myxine australis) was the most frequently encountered of the deep-sea fishes (50% of deployments), and while the Fueguian sprat (Sprattus fuegensis) was the most abundant fish species, its distribution was patchy. The Cape Horn and Diego Ramírez archipelagos represent some of the last intact sub-Antarctic ecosystems remaining and a recently declared large protected area will help ensure the health of this unique region.

Seasonal variation and community structure of fishes in the Mahananda River with special reference to conservation issues

This study was carried out in the Mahananda River from January to December 2013 with a view to determining the seasonal variation and community structure of fishes along with some conservation issues. Monthly sampling was carried out using traditional fishing gears and fishes were identified based on morphometric and meristic characters. A total of 4082 individuals of native fish species were captured, analyzed and classified into 62 species belonging to 46 genera, 25 families and 9 orders. Cypriniformes and Siluriformes were the dominant fish orders represented by 19 species each and the most abundant family was Cyprinidae (14 species). In addition to indigenous individuals, 9 individuals of 2 exotic fish species (Hypophthalmichthys molitrix and Pangasius hypophthalmus) were also recorded. Among three sampling sites, S-1 was the most diversified in terms of not only the number of individual fish but also the number of species present represented by mean (±SE) individuals of 151.50±25.22 and species of 25.58±3.91. Three distinct fish groups of fish families were revealed from the cluster analysis of similarity. To improve the situation, control of illegal fishing gears, establishment of sanctuaries and legal protection for threatened species are recommended.

Seasonal variation and community structure of fishes in the Mahananda River with special reference to conservation issues

This study was carried out in the Mahananda River from January to December 2013 with a view to determining the seasonal variation and community structure of fishes along with some conservation issues. Monthly sampling was carried out using traditional fishing gears and fishes were identified based on morphometric and meristic characters. A total of 4082 individuals of native fish species were captured, analyzed and classified into 62 species belonging to 46 genera, 25 families and 9 orders. Cypriniformes and Siluriformes were the dominant fish orders represented by 19 species each and the most abundant family was Cyprinidae (14 species). In addition to indigenous individuals, 9 individuals of 2 exotic fish species (Hypophthalmichthys molitrix and Pangasius hypophthalmus) were also recorded. Among three sampling sites, S-1 was the most diversified in terms of not only the number of individual fish but also the number of species present represented by mean (±SE) individuals of 151.50±25.22 and species of 25.58±3.91. Three distinct fish groups of fish families were revealed from the cluster analysis of similarity. To improve the situation, control of illegal fishing gears, establishment of sanctuaries and legal protection for threatened species are recommended.

Seasonal variation in species composition and abundance of demersal fish and invertebrates in a Seagrass Natural Reserve on the eastern coast of the Shandong Peninsula, China

Seagrass habitats are structurally complex ecosystems, which support high productivity and biodiversity. In temperate systems the density of seagrass may change seasonally, and this may influence the associated fish and invertebrate community. Little is known about the role of seagrass beds as possible nursery areas for fish and invertebrates in China. To study the functioning of a seagrass habitat in northern China, demersal fish and invertebrates were collected monthly using traps, from February 2009 to January 2010. The density, leaf length and biomass of the dominant seagrass Zostera marina and water temperature were also measured. The study was conducted in a Seagrass Natural Reserve (SNR) on the eastern coast of the Shandong Peninsula, China. A total of 22 fish species and five invertebrate species were recorded over the year. The dominant fish species were Synechogobius ommaturus, Sebastes schlegelii, Pholis fangi, Pagrus major and Hexagrammos otakii and these species accounted for 87% of the total number of fish. The dominant invertebrate species were Charybdis japonica and Octopus variabilis and these accounted for 98% of the total abundance of invertebrates. There was high temporal variation in species composition and abundance. The peak number of fish species occurred in August–October 2009, while the number of individual fish and biomass was highest during November 2009. Invertebrate numbers and biomass was highest in March, April, July and September 2009. Temporal changes in species abundance of fishes and invertebrates corresponded with changes in the shoot density and leaf length of the seagrass, Zostera marina.

Stream degradation, fish abundance and the potential viability of ornamental fisheries in south-western Cameroon

Fifteen sites on nine second- and third-order streams in the Mount Cameroon area, with varying degrees of human disturbance, were sampled during wet and dry seasons over 21 months in 2003–2005 to estimate their potential for sustainable exploitation of ornamental fishes. In total, 35 species of fish representing 22 genera and 14 families were captured. By biotope, fish populations per 20 m averaged 528 ± 318.5 fish (8.0 ± 3.02 species) in runs, 86 ± 60.9 fish (2.4 ± 1.06 species) in riffles and 819 ± 480.0 fish (7.8 ± 3.15 species) in pools. Riffles contained significantly fewer individuals and species than either runs or pools. Shannon's index was similar for runs and pools, averaging 1.646 ± 0.429 and 1.548 ± 0.345, respectively, but differed significantly for riffles, averaging 0.652 ± 0.473. There were no significant differences in number of individual fish, number of species or Shannon's index among stream order or season, reflecting the stability of these ecosystems throughout the year. Regression of number of fish per 20 linear m of stream, number of species and Shannon's index against a subjective scale related to stream degradation was significant. In particular, the polluted Limbe River sites had significantly fewer individual fish, fewer species and a lower Shannon index across all biotopes than other sites. Fishing efficiency of local gears was estimated at 27% for easily captured species and 14% for the more difficult ones, and could be used to make relative estimates of fish abundance as a means of monitoring changes in fish abundance. Although species diversity in south-western Cameroon was high, typical of tropical streams globally, total abundance was low, and therefore it is unlikely that a profitable ornamental fish trade could be sustained on the basis of fish captured exclusively from the wild.

Flow seasonality and fish assemblage in a tropical river, French Guiana, South America

The objective of this study is to verify the existence of a seasonal pattern of variation in the fish assemblages of a tropical river using taxonomic and functional descriptors. Fish were sampled using gillnets at two sites on the Comté River, a large-sized river 254.8 km long, flowing entirely through rainforest areas of French Guiana. Samplings were conducted every other month from August 1998 to July 2000. Four types of fish assemblage descriptors were used: the species descriptor (number of individual fish of each species in the sample); the family descriptor (number of individual fish of each family in the sample); the trophic descriptor (distribution of the fish biomass in each feeding guild) and the specific maximum observed size - MOS (number of individual fish in each of four classes of MOS: < 100 mm; 101-200 mm; 201-300 mm; > 300 mm). Results point out that changes in the fish assemblage are related to water level oscillations. The role of migration seems to be weak and is limited to trophic displacements characteristic of few species. In the low-water season, characterized by weak water level oscillation, fish species and families belonging to piscivorous or aquatic invertivorous guilds were predominant, whereas in the high-water season the environment is submitted to strong variations caused by fast and large water level oscillations, and the fish assemblage was characterized by species or families with an opportunistic omnivorous diet.

Camera Configuration and Use of AUVs to Census Mobile Fauna

There is a diversity of shapes and sensor configurations used in the design of autonomous underwater vehicles (AUVs). Cameras and lighting (for both still and video imaging) are common sensor systems and have traditionally been configured to produce orthogonal images of the seafloor. Such imagery provides invaluable small-scale, high-resolution data for studies of seafloor geology and sessile invertebrate communities. However, using orthogonal imagery to census the diversity of mobile fauna has limitations caused by avoidance. A simple analysis using species-individual curves demonstrated that species richness was generally lower in surveys using orthogonal images when compared to forward-looking oblique images despite encountering the same number of individual fishes. This pattern was consistent when contrasting data from separate AUV and ROV surveys at boulder reefs in the Gulf of Maine as well as from down-looking and forward-looking cameras simultaneously collecting video imagery from a camera sled in a variety of habitats. These results indicate a need to evaluate the effects of camera configuration on the performance of abundance and diversity indicators developed from image data acquired using AUVs and other vehicles. Further, we recommend that AUV designers endeavor to accommodate oblique angles for cameras and associated lighting within vehicle design parameters in order to support missions that improve detection of mobile fauna.