Local Fish Species Research Articles

Fostering fisheries futures: the promise of localized stewardship education in Nunatsiavut

Nunatsiavut is a self-governing Inuit territory in northern coastal Labrador, where cultural knowledge and social values are incorporated into co-managed subsistence and commercial fisheries. Snow crab (Chionoecetes opilio), known as Putjotik in Inuttitut (the Nunatsiavut dialect of Inuktitut), is a co-managed fishery through the Torngat Joint Fisheries Board (TJFB) and plays a crucial role in sustaining the community of Makkovik. Arctic Char (IKaluk) is also harvested in co-managed subsistence and commercial fisheries, and is a staple in local economies and culture. In 2022, the TJFB partnered with Inuit educators to foster youth stewardship in a project called Paigitsiaguk. The Paigitsiaguk project bridges Inuit and scientific knowledge to nurture cultural values and environmental stewardship through providing place and land-based resources to educators. The project team created a comprehensive database of curriculum outcomes required by the Newfoundland and Labrador school system, and then designed culturally relevant learning activities that presented Inuit knowledge with science and social studies for students in Nunatsiavut. These resources include learning activities that are organized into education kits: one of which is centered on Putjotik and another on IKaluk. The Putjotik kit has 23 activities tailored to meet grade-specific learning outcomes, while the IKaluk kit provides 12 place-based learning activities appropriate for multiple grade levels. By providing localized and culturally relevant education resources to teachers that revolve around stewarding local fish species and their ecosystems, youth are connecting to their communities and to the coastal environment. Educational resources and learning activities reflect Inuit and scientific knowledge systems, and position teachers as facilitators to encourage students to learn from the land and Elders, knowledge holders, fishers, scientists, and managers. This paper reflects the promising futures that this work can contribute to; from facilitating intergenerational knowledge transmission from knowledge holders to youth, to encouraging self-determined stewardship activities that encourage care for the ocean and its fisheries.

Unseen riverine risk: Spatio-temporal shifts of microplastic pollution and its bioavailability in freshwater fish within the Ikopa River urban system.

Growing concern over microplastic pollution, driven by their widespread accumulation in the environment, stresses the need for comprehensive assessments. This study investigates the spatial and temporal distribution of microplastics in the Ikopa River (Antananarivo - Madagascar), which flows through a densely populated area, and examines their correlation with contamination levels in local fish species. By analyzing upstream and downstream stations across wet and dry seasons, only a notable increase in microplastic concentration downstream during the wet season was observed, ranging from 138.6 ± 9.0 to 222.0 ± 24.5 particles m-3, with polyethylene-co-vinyl acetate being the predominant polymer at 62.3 ± 5.13% of the total sampled polymers. This distribution underlines the impact of urban activities on pollution levels. Fish species, gambusia and Nile tilapia, were assessed for microplastic occurrence in gills and gastrointestinal tracts. Higher contamination rates were found in gambusia, enlightening the influence of feeding behaviour and fish habitat on microplastics contamination. Ingestion of microplastics directly from the water column was evident in both species, with the detection of high-density plastics such as polytetrafluoroethylene and polyvinyl chloride suggesting likely sediment contamination. This research highlights the widespread contamination of aquatic environments and its direct impact on local wildlife, pointing to a clear requirement for effective pollution management strategies.

Growth optimalization of bileh fish seeds (Rasbora sp.) through different feeding frequencies

Bileh fish is a type of freshwater fish that is sought after by the people of Aceh because it has a delicious taste and is quite tasty. Bileh fish is a local fish species that has the potential to be developed as an aquaculture commodity and its population must be preserved from overfishing. The aim of this research was to determine the effect of different feeding frequencies on the growth of bileh fish fry (Rasbora sp.). This research used a non-factorial completely randomized design (CRD) method consisting of 4 treatments and 3 replications each, namely the frequency of feeding 1 time/day (P1), feeding 2 times/day (P2), feeding 3 times/day day (P3) and feeding 4 times/day (P4). The feed given is commercial feed PF 500 with 39% protein. The parameters observed included survival rate, length growth, weight growth, daily growth rate, feed efficiency and water quality. The results showed that different feeding frequencies had no significant effect on survival rate, absolute length and daily growth rate of bileh fish (Rasbora sp.). However, it has a real effect on weight growth and feed efficiency. The best feeding frequency to optimize the weight growth of bileh fish (Rasbora sp.) is in the P3 treatment with a frequency of 3 times/day.Keywords: Feed Efficiency; Feeding Frequency; Growth; Rasbora

DETERMINATION OF FISH DIVERSITY IN THE ROCKY HABITAT AROUND MERSIN BOĞSAK ISLAND (NORTHEAST MEDITERRANEAN) BY VISUAL CENSUS METHOD

This study was conducted in the rocky habitat of Boğsak Island in Mersin Bay in November, March and July, representing the fall, spring and summer months of 2022-2023, by scuba diving between 0-18 m depth for approximately 40 hours. The Go-Pro Hero 12 black camera was used in the study. In the study, the structure of the fish community of the rocky bottom habitat of Boğsak Island in Mersin Bay was determined, and the seasonal availability, abundance, feeding status, and distribution of local and non-native fish species were determined. Sampling was carried out using the underwater visual counting method, and surveys were made along a linear line. Shannon-Weiner Diversity Index (H'), Homogeneity and Relative Diversity Index Evennes (J) and Species Richness Index Margalef Rhichnes (D) were used to determine the species diversity. The distance of the relationship between the data was determined with N-MDS, one of the multidimensional scaling analyses. The Euclidean formula was used to determine the distances of coordinates in the scaling. Principal component analysis was used to classify species based on the number of individuals. A total of 29 fish species, including 28 bony fish species belonging to 15 families and 1 cartilaginous Gymnura altavela (Linnaeus, 1758), were identified in the study area. The richest family in terms of species diversity was Sparidae (6), followed by Mullidae (3), Serranidae (3), Tetraodontidae (2), Soleidae (2), Labridae (2) and other families with 1 species each. Of the fish species identified throughout the year in the study area, 52% were Atlantic, 37% were Indo-Pacific and 11% were cosmopolitan. It was found that 41% of the fish species were invertivores, 22% carnivores (feeding on fish and invertebrates), 18% omnivores, 11% planktivores, 4% herbivores and 4% piscivores. Torquigener flavimaculosus in summer, Cheilodipterus novemstriatus in spring, and Chromis chromis in fall were the most abundant species. According to the Shannon diversity index (H'), the highest species diversity was found in the fall (H'=2,956), followed by spring (H'=2,501) and summer (H'=2,458). Homogeneity and relative diversity index Evennes (J) was determined as J=0.642 in spring, J=0.531 in summer and J=0.800 in fall. The species richness index Margalef Rhichnes (D) was highest in autumn (d=4.804), then in summer (d=3.917) and lowest in spring (d=3.632). This is the first study to investigate the structure of rocky habitat fish communities in the northeastern Mediterranean, which shows a dynamic structure in terms of biodiversity, and is expected to contribute to researchers working in this field.

Microplastics have additive effects on cadmium accumulation and toxicity in Rice flower carp (Procypris merus)

Procypris merus, a local fish species found in Guangxi, China is often exposed to both microplastics (MPs) and Cd. However, it remains unclear how these two pollutants affect P. merus. Therefore, we investigated the effects of MPs on Cd accumulation in P. merus. To this end, P. merus was separately exposed to Cd and MPs (500 μg/L) or their combination for 14 days. We found that MPs enhanced Cd accumulation in liver and gills of P. merus. Further, both the single-contaminant (MP and Cd) and combined treatments resulted in lesions in these two tissues, with more severe damage associated with the combined treatment. Even though the effect of MP on the antioxidant defense system of P. merus was limited, the Cd-only and combined treatments considerably affected the antioxidant parameters of P. merus, with the combined treatment showing a stronger effect. GO and KEGG analyses revealed that the differentially expressed genes (DEGs; TNF-related apoptosis-inducing ligand receptor, trail-r) in the Cd-only treatment group were enriched for immune-related GO terms and cell growth and death related pathways, indicating that Cd toxicity affected immune defense in P. merus. The MP-only treatment downregulated DEGs (acyl-CoA synthetase long chain family member 1a, acsl1a) related to lipid metabolism, possibly leading to lipid accumulation in the liver. The combined treatment also upregulated DEGs (aspartate aminotransferase 1, ast 1) associated with immune-related GO terms and amino acid metabolism pathways, suggesting that it affected immune function in P. merus, thereby negatively impacting its health. Results indicated that MPs have additive effects on Cd accumulation and toxicity in rice flower carp. Consequently, MPs ingested by P. merus can promote Cd accumulation, more adverse effects on the health may occur after combined exposure, which can eventually reach humans through the food chain and pose potential risks to human health.

STRATEGI PENGEMBANGAN EKOWISATA BUKIT BATU, DUSUN SUNGAI LUAR, DESA TIWINGAN BARU, KECAMATAN ARANIO, KABUPATEN BANJAR, PROVINSI KALIMANTAN SELATAN

This research aims to determine what strategies can be taken in managing Bukit Batu Ecotourism. This is because Bukit Batu Ecotourism has considerable potential, including biotic potential such as flora and fauna as well as abiotic potential such as mountains, hills, rivers, forests and lakes which of course have an attraction for tourists. The analytical method used in this research is a qualitative descriptive method. Where this research activity was carried out in natural and uncontrived object conditions, then the data obtained was analyzed using SWOT analysis. the SO strategy in order of priority which is described as follows: (1) Create tourist attractions and attractions that display ecological potential and diversity of flora and fauna such asaviary (giant bird cages), a mini zoo, an aquarium that accommodates local fish species and a miniature Borneo rainforest featuring endemic plant species. (2) Make a viewing tower to enjoy the beautylandscape mountains and lakes as a whole. (3) Empowering the surrounding community in managing Ecotourism such as retribution officers, cleaning officers and security officers. (4) Make plans for the development of facilities and infrastructure based on the most important priorities, such as telecommunication and internet signal booster towers, repair of roads that are still damaged and street lighting. (5) Increase safety warning boards. And (6) Empowerment of BUMDES (Village-Owned Enterprises) with clear work contracts so that they can have an impact on increasing the economy of the surrounding community, such as providing boat rental services, tour guides, bicycle/tent rental and selling souvenirs.

Oil spill in an amazon blackwater environment: Biochemical and physiological responses of local fish species

The accidental spill of petroleum asphalt cement (PAC) in São Raimundo (SR Harbor, located on the Rio Negro (Manaus, Amazonas, Brazil) was monitored through the analysis of polyciclic aromatic hydrocarbons (PAHs) in water and a set of biomarkers in fishes (exposure biomarkes: PAHs-type metabolites concentrations in bile; the activities of ethoxyresorufin-O-deethylase (EROD), glutathione-S-transferase (GST), catalase (CAT), superoxide dismutase (SOD), and glutathione peroxidase (GPx) in liver. Effect biomarkers: lipid peroxidation concentration (LPO) in liver, acetylcholinesterase activity in brain, and genotoxic DNA damage in erythrocytes). Two fish species, Acarichthys heckelii and Satanoperca jurupari, were collected 10, 45, and 90 days after the PAC spill in São Raimundo. At the same time, fish were collected from the Tupé Sustainable Development Reserve (Tupé) which served as a reference area. The sampling periods were related to the rising waters of the natural flood pulse of the Rio Negro. Higher concentrations of PAHs in water were observed at 10 and 45 days and returned to the values of TP 90 days after the PAC spill, a period in which harbor waters rose about 0.2 m. Unlike the PAHs in water, biomarker responses in both fish species significantly increased following the PAC spill in SR. Hepatic ethoxyresorufin-O-deethylase (EROD), PAH-like metabolites in bile, and erythrocyte DNA damage increases, together with inhibition of acetylcholinesterase (AChE) activity in the brain were the most evident responses for both fish species. The calculated pyrolytic index showed mixed sources of PAHs (petrogenic and pyrolytic). The applied PCA-FA indicated important relationships between dissolved organic carbon (DOC) and PAHs concentrations in water, where DOC and PAHs concentrations contributed to biomarkers responses for both fish species in all collection periods.

Analysis of Fatty Acids and Amino Acids of Three Local Freshwater Bagridae Fish Species in the Kampar Kanan River, Indonesia, for Food Security.

Fish have become an irreplaceable dietary source of animal protein, especially among households with low socioeconomic status in rural and urban areas of Indonesia. This study is aimed at analysing the proximate composition, minerals, fatty acids, and amino acids of three local Bagridae fish species in the Kampar Kanan river, Indonesia. The standard AOAC method was employed to examine the proximate composition of the carcass, and the analysis of amino acids and fatty acids was conducted through HPLC and GC-MS, respectively. The mineral content was determined using AAS. The nutrient composition results of Hemibagrus nemurus, Hemibagrus wyckii, and Mystus nigriceps revealed that the protein content was 24.26%, 22.57%, and 21.39% (% dry weight), whereas the total lipid content was 6.64%, 7.47%, and 7.75%, respectively. Regarding mineral contents, the calcium levels ranged from 1.49 to 1.66 mg/g, iron levels from 28.35 to 40.36 μg/g, and zinc levels from 24.03 to 54.46 μg/g. Among the fatty acids, palmitic acid was the most abundant in all three species, accounting for 25.59-30.70% of the total fatty acids. Additionally, significant amounts of C18:1 (oleic acid), C18:0 (stearic acid), and C20:4 (arachidonic acid) were also detected as primary fatty acids. The calculated atherogenic index values in the three species of Bagridae fish ranged from 0.73 to 0.99, while the thrombogenic index values varied between 0.54 and 0.75. The predominant amino acids found in the three species of Bagridae fish were glutamic acid with their concentrations ranging from 9.10 to 24.34%. These results indicate that consuming the meat of these three freshwater Bagridae fish species caught in the wild does not pose any health risks to consumers. They can be considered a safe and suitable food source with good nutritional quality.

Atractosteus spatula, a first-record exotic alligator gar from Dal Lake in Kashmir, India, poses a potential threat to local fish species

Atractosteus spatula, a first-record exotic alligator gar from Dal Lake in Kashmir, India, poses a potential threat to local fish species

Assessment of the utilization status of fourfinger threadfin (Eleutheronema tetradactylum) in the waters of Dumai City, Riau Province

One of the local fish species exploited in the waters of Dumai is fourfinger threadfin (Eleutheronema tetradactylum). The purpose of this research is to analyze the maximum sustainable yield, optimal efforts, and utilization levels of fourfinger threadfin. Data on catches and efforts were collected from the annual reports of the Department of Fisheries Dumai City over a period of ten years. The results of the analysis using the Walter-Hilborn model indicate that the maximum sustainable yield of fourfinger threadfin is 234 ton year-1, and the optimal effort (Eopt) is 404 unit year-1. The average utilization rate of fourfinger threadfin from 2014 to 2023 is 28 percent. The resource is currently moderately exploited (25-75%), indicating that the stock has been harvested close to its maximum sustainable yield value. It is advisable to increase fishing efforts without compromising the sustainability of fourfinger threadfin in the waters of Dumai City.

Hedonic test and chemical organoleptic and chemical characteristics of cork and toman fish emping

Local fish species from the waters of South Kalimantan that are a source of protein and high in albumin are cork fish and toman fish. In an effort to increase the value added and consumption of both fish, it is necessary to diversify the product, for example by processing them into fish emping. Emping is a type of round and thin snack generally made from melinjo seeds, which are flaked, dried and then fried. The aim of this study was to determine the organoleptic and chemical characteristics of cork and toman fish emping. This study consisted of 2 treatments, namely the cork fish puff and the toman fish puff. To determine the difference between the two treatments, data analysis was carried out using independent t-test with test parameters including yield calculation, hedonic test (taste, colour, aroma and texture) and chemical test (water, ash, protein, fat, carbohydrate, fibre, energy, TKE and TKP). Based on the results of the t-test, it is known that the organoleptic characteristics of the two empings show a significant difference, with the cork emping being more favourable than the toman emping. The chemical characteristics did not show any significant difference. In conclusion, the yield characteristics, moisture content, ash, protein, fat, carbohydrate, fibre, energy, energy sufficiency level (TKE) and protein sufficiency level (TKP) of cork fish cake were 4.07%, 66.66%, 2.67%, 7.22%, 0.95%, 319.52 kcal, 20.97% and 202.00% respectively with a yield of 10.10%. For toman, the values were 19.29%, 4.31%, 66.89%, 2.55%, 6.96%, 1.02%, 318.37 kcal, 20.54% and 202.69% with a yield of 10.83%. Thus, both cork and toman fish cake are high protein products.

Foraging behavior and sea ice-dependent factors affecting the bioaccumulation of mercury in Antarctic coastal waters

To elucidate the potential risks of the toxic pollutant mercury (Hg) in polar waters, the study of accumulated Hg in fish is compelling for understanding the cycling and fate of Hg on a regional scale in Antarctica. Herein, the Hg isotopic compositions of Antarctic cod Notothenia coriiceps were assessed in skeletal muscle, liver, and heart tissues to distinguish the differences in Hg accumulation in isolated coastal environments of the eastern (Chinese Zhongshan Station, ZSS) and the antipode western Antarctica (Chinese Great Wall Station, GWS), which are separated by over 4000 km. Differences in odd mass-independent isotope fractionation (odd-MIF) and mass-dependent fractionation (MDF) across fish tissues were reflection of the specific accumulation of methylmercury (MeHg) and inorganic Hg (iHg) with different isotopic fingerprints. Internal metabolism including hepatic detoxification and processes related to heart may also contribute to MDF. Regional heterogeneity in iHg end-members further provided evidence that bioaccumulated Hg origins can be largely influenced by polar water circumstances and foraging behavior. Sea ice was hypothesized to play critical roles in both the release of Hg with negative odd-MIF derived from photoreduction of Hg2+ on its surface and the impediment of photochemical transformation of Hg in water layers. Overall, the multitissue isotopic compositions in local fish species and prime drivers of the heterogeneous Hg cycling and bioaccumulation patterns presented here enable a comprehensive understanding of Hg biogeochemical cycling in polar coastal waters.

Exploring foraging preference of local fish species towards non-indigenous fouling communities near marinas: Insights from Remote Video Foraging System (RVFS) trials

Non-indigenous species (NIS) spread from marinas to natural environments is influenced by niche availability, habitat suitability, and local biotic resistance. This study explores the effect of indigenous fish feeding behaviour on NIS proliferation using fouling communities, pre-grown on settlement plates, as two distinct, representative models: one from NIS-rich marinas and the other from areas outside marinas with fewer NIS. These plates were mounted on a Remote Video Foraging System (RVFS) near three marinas on Madeira Island. After 24-h, NIS abundance was reduced by 3.5 %. Canthigaster capistrata's preference for marinas plates suggests potential biotic resistance. However, Sparisoma cretense showed equal biting frequencies for both plate types. The cryptogenic ascidian Trididemnum cereum was the preferred target for the fish. Our study introduces a global framework using RVFS for in-situ experiments, replicable across divers contexts (e.g., feeding behaviour, biotic resistance), which can be complemented by metabarcoding and isotopic analysis to confirm consumption patterns.

Homogeneity in terrestrial land cover is reflected in fish diversity patterns in a Chinese river system

AbstractIn river systems worldwide, land cover changes have been identified as major drivers of biodiversity change. Quantifying how terrestrial land cover impacts riverine diversity requires local biodiversity assessments. In this study, we investigated the association of terrestrial land cover and the corresponding riverine fish species communities using eDNA‐metabarcoding in the Chinese Shaying River basin. This basin is home to about 37 million people and is largely dominated by a mix of intense agriculture and urban areas, creating a relatively homogeneous, intensely used landscape. We investigated whether the homogeneous landscape is mirrored in the composition and structure of fish communities in the river network. We sampled eDNA in spring and fall of 2018, amplified it with a primer designed for local fish species and used operational taxonomic units (OTU) assigned to fish as proxy for diversity. Furthermore, we used redundancy analysis, general linear models, and distance decay curves to assess the effects of land cover on fish communities. We found that the Shaying River showed relatively high basin‐wide richness (63 OTU) and seasonal differences in local richness, but limited community differentiation. Variations in alpha‐ and beta‐diversity, measured as local OTU richness and pairwise distance‐decay across the basin were low. Redundancy analysis showed only a weak association between observed aquatic communities and their terrestrial surroundings in a 10 km buffer upstream. The lack of community differentiation assessed by eDNA metabarcoding reflects the homogeneous and intense land‐use in this basin.

Survey on performance of vertical slot and nature-like fishways at Angu hydropower station, Southwest China

To restore dam-blocked natural fish migratory passages, a growing number of artificial fishways have been built in water conservancy and hydropower projects in China. The Angu hydropower station involved diverse important fish habitats in the lower reaches of the Daduhe River in Southwest China. Therefore, a vertical slot fishway (VSF) and a nature-like fishway (NLF) were built near the backwater area of the reservoir to connect the upstream and downstream habitats. Hydrodynamic and aquatic ecological surveys were conducted after the completion of the project to estimate the fish passing effect of the two fishways. The results indicated that both fishways were in effective operation and could maintain the desired hydrodynamic conditions and be used by several local fish species. During the survey, 149 fish from 15 species and 111 fish from 17 species were captured by the traps in the VSF and NLF, respectively, while 1 263 fish from 27 species were found in the downstream area. Some species captured in the VSF were not found in the NLF, and vice versa, which implied the different preferences of fish. Meanwhile, 3 789 signals including 2 099 upward ones and 1 690 downward ones were monitored with an ultrasonic fish detector at the inlet of the VSF. These findings revealed the characteristics of fish species observed in and near the fishways and provided valuable insights into the different fish passing capabilities of VSF and NLF.

Trace metal exposure and risk assessment of local dominant fish species in the Beijiang River Basin of China: A 60 years' follow-up study

The Beijiang River, one of the Pearl River tributaries located in Guangdong, China, plays a critical role in providing water and fishery resources for the Pearl River Delta and receiving a large amount of domestic and industrial wastewater. However, due to the lack of historical monitoring data, we are unable to fully understand the relationship between the industrial and agricultural development and the environment. In this study, fish specimens collected from the Beijiang River Basin over a span of nearly 60 years (1963–2021) are used as research objects and the concentrations of ten trace metals (TMs) in two locally dominant fish species were determined by an inductively coupled plasma mass spectrometer. The human health risks caused by consuming fishes were assessed. Results show a correlation between the levels of TMs in fish muscle and the degree of industrialization. The concentrations of Cr, Mn, Ni, and Cu peaked during the period of 1981–1983, when China's industrial development was rapidly expanding while the environmental protection facilities were incomplete. However, with the implementation of Ecological Civilization policy, the levels of Cr, Mn, Ni, Cu, Cd, and Ba showed a downward trend in the period from 2018 to 2021. Cu concentrations in both fish muscle and viscera exhibit analogous change patterns across different periods, indicating that Cu serves as a significant indicator of TM pollution in the Beijiang River Basin. The presence of TMs in fish muscle often exhibits long-term enrichment, while those in the viscera demonstrate short-term accumulation. Based on the estimated daily intake, the target hazard quotient (THQ), and total THQ value, the overall health risk associated with TMs in fish from the Beijiang River Basin is low. However, certain TMs in the fish rebounded during 2018–2021, posing a potential risk for aquatic biology and ecosystems, which is worth our attention.

An Experimental Study of Fish Movement with Turbulent Kinetic Energy along the Pools of A Vertical Slot Fish Pass

Bangladesh is a land of river which is situated in the delta of the Ganges-Brahmaputra-Meghna (GBM) Rivers which are three of the largest rivers of the world. These rivers provide an arterial transportation network for fish movement. Fish migration depends on flow characteristic and surrounding flood plain connected to rivers. In recent time for flood control in monsoon and water storage in lean period a lot of structure has been built along and across the river [77]. As a result the natural sequence of flooding in floodplain of Bangladesh, food chain and life cycle of natural fish and other aquatic species has become under sever threat [64]. In this research an experimental approach has been carried out to understand the turbulence structures of the flow inside a laboratory flume with different local fish species. The structural set up consists of an adverse slope of 6% followed by a mild slope of 3.4%. The adverse slope is 2.54 m in length and the mild slope is 4.45 m in length. Total nine sets of experiments have been conducted. For each set of experiments, data points were distributed on a 10 cm (in the longitudinal direction) x 10 cm (in the transverse direction) grid at 0.6 hydraulic depth and 10 cm (in the longitudinal direction) x 20 cm (in the transverse direction) grid at 0.4 and 0.8 hydraulic depth. In this experimental setup turbulent kinetic energy and fish movement in all four pools will be observed. This experimental study consists of three types of fish species; Rui (Labeo rohita), Catla (Giberlion catla) and Mrigel (Cirrhinus mrigala) of fry size (1-2 cm body length), fingerline size (7-10 cm) and juvenile size (10-20 cm) have been selected for studying. The flow from slot travels through the center of the pool to the next slot with two recirculation region on either side of the jet. At the pool opening the flow appear almost in the form of a shooting jet. There are similarities with turbulence characteristics in each case. Fishes have avoided high turbulent kinetic energy area in the contour map. The comparison shoes the area with low turbulent kinetic energy was most suitable for fishes to pass the pools or taking rest inside the pools. The results may be useful insight on the turbulence characteristics of flow in the vertical slot fish pass and can be used to study fishes characteristic and also for guidance in the design of fish pass in the future.

Mercury accumulation and biomarkers of exposure in two popular recreational fishes in Hawaiian waters

Mercury (Hg) exposure has not been examined in many recreational nearshore fish species that are commonly consumed around the Hawaiian Islands. Specific gene transcripts, such as metallothionein (MET) and thioredoxin reductase (TrxR), can be used to examine Hg exposure responses in aquatic organisms. This study measured total mercury (THg) in four species from two groups of Hawaiian nearshore fishes: giant trevally (Caranx ignobilis, n = 13), bluefin trevally (C. melampygus, n = 4), sharp jaw bonefish (Albula virgata, n = 2), and round jaw bonefish (A. glossodonta, n = 19). Total Hg accumulation and abundance profiles of MET and TrxR were evaluated for muscle, liver, and kidney tissues. Total Hg in round jaw bonefish and giant trevally tissues accumulated with length and calculated age. In round jaw bonefish tissues, mean THg was greater in kidney (1156 ng/g wet mass (wm)) than liver (339 ng/g wm) and muscle (330 ng/g wm). Giant trevally muscle (187 ng/g wm) and liver (277 ng/g wm) mean THg did not differ significantly. Fish species in this study were compared to commercial and local fish species with state and federal muscle tissue consumption advisories based on THg benchmarks developed by the U.S. Food and Drug Administration (FDA) and Environmental Protection Agency (EPA). Both bonefishes had mean muscle THg that exceeded benchmarks suggesting consumption advisories should be considered. MET transcript in round jaw bonefish kidney tissue and kidney THg exhibited a marginally significant positive correlation, while TrxR transcript in liver tissue negatively correlated with increasing liver THg. These results contribute to our understanding of Hg exposure associated health effects in fish.

Importance of coastal vegetated habitats for tropical marine fishes in the Red Sea

Marine vegetated habitats such as seagrass, mangroves, and macroalgae are common along tropical coastlines globally and provide habitats for a diversity of fishes, including juvenile fish and species found on coral reefs. Understanding the use of these habitats by different fish species and life stages is fundamental to spatial planning, fisheries management, and conservation. While previous studies have focused on the habitat potential of seagrass, macroalgae, or mangroves for coral reef fish independently, it is important to consider their combined roles, as tropical seascapes are often mosaics of such habitats. In this study, we evaluated habitat associations across life stages for fish species in coral reefs, seagrasses, macroalgae, and mangroves in Saudi Arabia’s central Red Sea. Through in situ visual surveys, we documented 36% of local coral reef fish species in one or more vegetated habitats, with the fraction of coral reef species utilizing macroalgae or seagrass much greater than that of mangroves (29%, 18%, and 6%, respectively). Mangroves hosted mainly juvenile fish (83% of observed population) and macroalgae hosted the largest proportion of herbivores (39% of observed population), suggesting that each environment offers different combinations of resources (food and shelter), and a mix of these habitats could support biological connectivity across a seascape. Species targeted by local fisheries made up 37% of the species documented in vegetated habitats. The use of multiple habitat types by juvenile and commercially important fishes in the Red Sea underscores the need for a holistic approach to habitat protection.Graphical abstract

Balancing Physical Channel Stability and Aquatic Ecological Function through River Restoration

Vortex rock weirs (VRW) are often used in natural channel design applications to maintain channel form and function, provide physical channel stability, and enhance aquatic habitats. A balanced approach is required to address (often) conflicting goals of VRWs, which include providing erosion protection and grade control while facilitating fish passage for target species. This research evaluated a sequence of modified VRWs in a small-scale watercourse in Southern Ontario, Canada. To determine passage suitability for the target fish species, the water level, water temperature, and channel geometries at 10 VRWs and 11 adjacent pools were monitored under different water level conditions. The structural dimensions and velocity at each VRW were compared to the burst swim speed of local small-bodied fish species to determine fish passage suitability and identify the best practices for VRW design and construction. The results concluded that VRWs provided suitable passage for small-bodied fish species through gap and over-weir flow pathways, particularly during low water level conditions. Further, appropriate design considerations based on the VRW gradient, VRW width, keystone size, and pool length contributed to 100% fish ‘passability’ under all water level conditions. The methodology is provided for predicting the velocity and small-bodied fish passage suitability through VRWs, informing the best practices for VRW design and construction while balancing the requirements for channel stability and fish passage, and contributing to fish population management strategies.