Fish Of Different Sizes Research Articles

SIZE AND ORGAN-SPECIFIC VARIATIONS IN PROXIMATE COMPOSITION OF FRIGATE TUNA (Auxis thazard)

Different species of tuna are well-known seafood items for their economic importance and nutritional profiles. Tuna is a cheap marine fish of Bangladesh but is not popular with consumers compared to other coastal and marine fishes. In this study, the proximate composition of tuna (Auxis thazard) was compared based on their size and body portions because size and body portions might have a significant impact on the nutritional value of the fish. Three different sizes, i.e., ≤500 g, ≤750 g, and ≥1 kg, and three different body portions, i.e., head, middle, and tail, were subjected to study for proximate analysis. Standard methods (Kjeldal and AOAC) were followed for the determination of biochemical parameters. Among different sizes of fish, the highest average percentage of protein (23.07±0.82), lipid (2.80±0.41), and ash (1.62±0.12) were calculated in the ≥1 kg size group, and among different body portions, the highest average percentage of protein (23.03±0.91), ash (1.62±0.09), and lipid (2.85±0.39) were calculated in the muscle from the middle portion of the fish. The highest average percentage of moisture (73.91±0.95) was found in the tail portion of the small-sized group. This study revealed that the comparatively larger fish and the middle portion of the body are nutritionally rich compared to the other sizes and body parts. Therefore, it is of utmost importance to raise awareness among consumers to ensure adequate nutrition at a cheap price.

Farmed Atlantic salmon (Salmo salar L.) avoid intrusive objects in cages: The influence of object shape, size and colour, and fish length

Underwater vehicles and other mobile platforms are seeing increased use as tools within fish farming, particularly due to current trends towards Precision Farming practices, and more exposed farming sites. Although many of the applications of such tools (e.g., net cleaning and inspection) have become well established industrial practices, it is largely unknown how much such operations disturb the fish and the consequence of this disturbance. In this study, we explored this by exposing Atlantic salmon in commercial net cages to intrusive objects and monitoring the distribution of fish around these using on-board 360-degree sonars. Six different object designs were tested covering variations in size, shape, and colour, which are important static characteristics of underwater vehicles/platforms. The sonar data was first aggregated into images containing the Cumulative Fish Presence over 1-, 5- and 10-min periods to provide a more robust foundation for further analyses. By training a deep learning based method using UNet++ architecture to automatically segment the fish distribution patterns, the mean distance between the inner perimeter of the fish distribution and the object was assessed. Results from the study implied that fish keep greater distances to larger objects. There was, however, no clear impact of the shape. Regarding the effect of colour, fish kept greater distances to yellow than to white objects. When comparing results from tests on fish of different size, data indicate a positive linear relationship between fish weight (age) and distance to an object, that can be expressed as an avoidance distance of an average 3.8 body-lengths. Our findings provide new fundamental knowledge on the dynamics between the fish and objects such as vehicles or other mobile platforms in fish farms, and thus provides valuable insights that can be useful when designing such tools specifically for aquaculture.

Effect of body weight on the nutrient composition of the muscle and skin tissues of Oncorhynchus mykiss

To provide basic research data for the processing and comprehensive utilization of triploid rainbow trout, we studied the nutritional quality of muscle and skin tissue of different sizes of fish (1250.10 ± 1.22 g, 2555.31 ± 1.32 g, and 3823.10 ± 1.44 g). The results showed that the proportion of skin and muscle was the highest when fish body size was 2555.31 ± 1.32 g. In muscle, lysine content was the highest and methionine content was the lowest among the essential amino acids (EAAs). Glutamic acid content was the highest and glycine content was the lowest among all umami-related amino acids. With increasing size, EAA, D-aspartic acid (DAA), and total amino acid (TAA) levels first increased and then decreased. The Met + Cys group contained the most restricted amino acids in the skin and muscle, and 2555.31 ± 1.32 g triploid rainbow trout had better amino acid balance and the best nutritional value. Of the essential minerals, Na, Mg, and K were the most abundant. According to Dietary Reference Intakes (DRI), Mg, Fe, and Zn can provide higher nutritional quality. Finally, the results showed that nutritional quality was highest in the muscle of the intermediate-sized triploid rainbow trout.

A Comparison of the Physiological Responses to Heat Stress of Two Sizes of Juvenile Spotted Seabass (Lateolabrax maculatus)

Temperature affects the metabolism of fish, and fish of different sizes have different tolerances to temperature. The aim of this experiment was to compare two sizes of juvenile spotted seabass, Lateolabrax maculatus (with average weights of 57.91 ± 11.57 g and 13.92 ± 2.77 g, respectively) for changes in physiological, biochemical, and molecular mechanisms under acute heat stress. Experimental fish were exposed to acute temperature increasing from 23 °C to 32 °C, and the mortality rate was noted at various heat stress exposures (0, 3, 6, 12, 24, 48, and 72 h). Moreover, serum and liver were obtained before and after heat stress. The activities of aspartate aminotransferase (AST), alanine aminotransferase (ALT), superoxide dismutase (SOD), malondialdehyde (MDA), lactic acid (LD), lactate dehydrogenase (LDH), glucose, and hepatic glycogen, and the expression of heat shock proteins (HSP70, HSP90) and apoptosis-related genes (BAX, caspase-3) in two sizes of spotted seabass were measured. Results showed that the contents of AST, ALT, SOD, MDA, LD, and glucose as well as the expression level of BAX and mortality were higher in large spotted seabass than in small spotted seabass within 12 h. These results indicate that the large spotted seabass had higher levels of oxidative stress and more severe liver damage, resulting in a higher mortality. Furthermore, the HSPs expression level of small spotted seabass was higher and the mortality was lower than that of large spotted seabass. Therefore, we considered that the large spotted seabass has lower levels of HSPs expression, causing their physiological response to be elevated to resist heat stress. In conclusion, spotted seabass with larger size has a poorer tolerance to heat stress compared with spotted seabass with smaller size. The smaller fish size was possibly resistant to heat stress by regulating the HSPs expression level in a more active extent.

Evidence of ontogenetic partitioning of restored coastal habitat by a generalist sportfish

Coastal and estuarine habitats that provide crucial nursery areas for many economically and ecologically important fish species are in decline. Restoration of benthic habitats can improve fish populations, biomass, and feeding opportunities, but there is limited research on how restoration impacts growth and survival with ontogeny. To address this knowledge gap, here we examine the biometrics (size, biomass, and body condition), recruitment, size structure, and trophic shifts of a sportfish (mangrove snapper, Lutjanus griseus) at restored oyster reefs and stabilized living shorelines to better understand how fish use restored habitats as they grow. Biomass and body condition of L. griseus juveniles and subadults, and post‐settlement recruitment, at restored/stabilized sites was similar, and in some cases greater than natural sites, correlating with benthic habitat, reef location, and lunar phase at oyster reefs. Living shorelines exhibited greater recruitment potential, while oyster reefs supported more juveniles and subadults, as evidenced by differences in fish size and biomass between habitats. Dietary overlap implies subadult L. griseus likely foraged across habitats more than juveniles, while there was greater diet similarity within habitats. Furthermore, ontogenetic shifts also occurred within oyster reef habitats, highlighting the importance of quality habitat to support various sportfish life stages, which can be achieved through restoration. These findings suggest life history attributes can be indicators of habitat restoration success, and specifically provide actionable science to guide the development of more effective strategies for restoring inshore nursery habitats and thus augment production of offshore reef fisheries.

Acute hydrogen sulfide exposure in post-smolt Atlantic salmon (Salmo salar): Critical levels and recovery

Despite the importance of Atlantic salmon in marine aquaculture production systems, remarkably little is known about the effects of hydrogen sulfide (H2S) on the physiology of the species. In recent years, mass mortalities of Atlantic salmon have been reported in recirculating aquaculture systems (RAS) due to acute H2S exposure. This highlights the importance of obtaining a better understanding of tolerance thresholds and metabolic responses to this toxic gas. The toxicity of H2S is exerted at the level of the mitochondria, where impairment of the enzyme cytochrome c oxidase inhibits cellular respiration. Because H2S depresses oxygen uptake (MO2), intermittent flow-through respirometry, a common method for assessing the metabolic response to various stressors in fishes, is a suitable method to determine concentration thresholds for when H2S affects the metabolism of Atlantic salmon. During exposure trials, 3 size groups (range ⁓100-500 g) of fish were acclimated to control conditions to obtain baseline measurements, whereafter they were exposed to progressively increasing H2S concentrations (0.53 ± 0.14 μM h−1) until MO2 decreased below the standard metabolic rate or loss of equilibrium occurred, which we considered to be the critical H2S concentration (H2Scrit). Fish were then allowed to recover in H2S free water to determine the excess oxygen consumption (EOC) following H2S exposure. The results show that Atlantic salmon have a lower tolerance to H2S than previously estimated, with a mean H2Scrit of 1.78 ± 0.39 μM H2S, which was independent of size. During recovery, the estimated EOC greatly exceeded the accumulated oxygen deficit (DO2) in all groups, and the small salmon had a significantly larger EOC. While the magnitude of the EOC was greater for small salmon, it did not differ in duration (recovery time) among the different sizes of fish. The larger EOC showed that H2S exposure had a greater effect on the recovery phase of the small salmon, and exposure to H2S may leave the fish more vulnerable to other stressors post-exposure. This study provides specific values that underline the sensitivity of Atlantic salmon to acute H2S exposure and emphasizes the importance of the aquaculture industry to implement mitigating strategies for the occurrence of H2S at production facilities.

Using a novel biologging approach to assess how different handling practices influence the post-release behaviour of Northern Pike across a wide range of body sizes

There is a growing body of research focused on how angled fish respond to catch-and-release (C&R). However, most of those studies do not span a wide range of body sizes for the targeted species. Physical injury and physiological responses to C&R can be size-dependent, and methods used for landing fish of different sizes vary. As such, studying the response to C&R across a range of fish sizes may help inform best practices that improve outcomes for released fish. Northern Pike (Esox lucius) widely ranges in body size. Anglers may land them by hand, cradle, or net, and they are often released voluntarily or to comply with regulations. We angled 25 Northern Pike (total length 620–1030 mm) from one population and recorded fight, handling, and unhooking times across landing methods (i.e., hand, cradle, net). Prior to release, a pop-off biologging package was temporarily affixed to each fish to monitor locomotor activity, depth, and water temperature during a 12-h period post-release to understand how the interaction of landing method and body size influenced post-release behaviour and short-term fate. Fight and handling time increased with increasing body size. Northern Pike landed with a cradle or net had shorter fight times but longer handling times, compared to fish landed by hand. Post-release locomotor activity was greater for larger fish and those landed with a net. Fish <775mm and landed by hand had greater locomotor activity than fish landed with a net or cradle, while fish >775mm landed by hand had reduced locomotor activity compared to fish landed with a net. There was no post-release mortality observed. Collectively, anglers should use a net for Northern Pike >775 mm to avoid long fight times and reduce post-release exhaustion, but also attempt to reduce the extent of handling associated with fish landed by net.

Environmental DNA persistence and fish detection in captive sponges.

Large and hyperdiverse marine ecosystems pose significant challenges to biodiversity monitoring. While environmental DNA (eDNA) promises to meet many of these challenges, recent studies suggested that sponges, as "natural samplers" of eDNA, could further streamline the workflow for detecting marine vertebrates. However, beyond pilot studies demonstrating the ability of sponges to capture eDNA, little is known about the dynamics of eDNA particles in sponge tissue, and the effectiveness of the latter compared to water samples. Here, we present the results of a controlled aquarium experiment to examine the persistence and detectability of eDNA captured by three encrusting sponge species and compare the sponge's eDNA capturing ability with established water filtration techniques. Our results indicate that sponges and water samples have highly similar detectability for fish of different sizes and abundances, but different sponge species exhibit considerable variance in performance. Interestingly, one sponge appeared to mirror the eDNA degradation profile of water samples, while another sponge retained eDNA throughout the experiment. A third sponge yielded virtually no DNA sequences at all. Overall, our study suggests that some sponges will be suitable as natural samplers, while others will introduce significant problems for laboratory processing. We suggest that an initial optimization phase will be required in any future studies aiming to employ sponges for biodiversity assessment. With time, factoring in technical and natural accessibility, it is expected that specific sponge taxa may become the "chosen" natural samplers in certain habitats and regions.

Protease and Amylase Activities of Javaen barb (Systomus rubripinnis Val.)

Studies on morphology, growth, and reproduction have been carried out on wild Javaen barb, but there was no information on its digestive capacity; therefore, the research was conducted to determine protease and amylase activities in the digestive tract. This study used a total of 50 barbs with body weights between 13.56 -128.93g / fish. The measurement of enzyme activity was carried out using the spectrophotometer method. The results showed that differences in fish size resulted in differences in protease activity, but not for amylase. Fish with a small size have a higher protease activity than fish with a larger size. The protease activity did not differ between pH 6.9 to 10.0 but was higher than pH 12.5. Protease activity also did not vary between the anterior and posterior intestine and between 30-50°C. Amylase activity also found no difference between the anterior and posterior intestine, but there was a difference in activity between temperatures of 30-50°C. In conclusion, protease activity occurs in a neutral to alkaline environment, and there were differences in protease activity between different body sizes but not between intestinal segments. Amylase activity occurs throughout the intestine and decreases at temperatures of 50°C.

Fish stock mass reduction is indicated in standard abundance and biomass estimates from gillnets and hydroacoustics

Gillnetting is a technique commonly used in relative abundance and biomass estimates of fish. However, due to its passive nature, the direct recalculation of the catch to reservoir volume or area is not trivial. This issue is often solved by using hydroacoustics, which provides information about fish density, though without the ability to distinguish species. However, the precision of such density estimates are also questionable. In this study, we estimated the abundance and biomass of dominant fish species before and after a biomanipulation program (fish removal) in 2020 using gillnetting and hydroacoustic surveys in a temperate reservoir. Between the two sampling periods, nearly 27,000 individuals (9000 kg) older than 0 + of bleak (Alburnus alburnus) and bream (Abramis brama) were removed during the biomanipulation program. Decreases in abundance and biomass estimates were expected for both techniques and both species. The gillnet decrease was 68% in CPUE (catch per unit of effort) and 48% in BPUE (biomass per unit of effort) for both species and all gillnets grouped together. Hydroacoustic observations showed a decrease of approximately 79% in abundance and 74% in biomass after fish reduction. Considering the numbers and biomass of fish removed, the absolute hydroacoustic estimates were underestimated for fish abundance but credibly estimated for biomass. The average weight of the fish taken was between the values of the fish caught with gillnets and the weights determined by hydroacoustics. In terms of results, both methods appear to be a suitable tool for estimating fish abundance and biomass in large inland waters, although the spatial and temporal distribution of fish of different sizes should be considered when using different sampling methods for fish monitoring.

Transcriptome analysis reveals the involvement of ubiquitin-proteasome pathway in the regulation of muscle growth of rice flower carp

Growth mechanism of economically important aquaculture species has aroused widespread interest among scholars. Rice flower carp (Cyprinus carpio), commonly cultured in rice-fish farming systems, shows wide variation in body mass at the same age, which limits the development of commercial aquaculture. In this study, muscle tissues from 20-month-old fish of different sizes were used for transcriptome analysis and muscle histological studies. The muscle histological analysis showed the muscle growth in rice flower carp main depends on the hypertrophic growth of muscle fibers. A total of 30,590 unigenes were generated by muscle trancriptome analysis, including 403 differentially expressed genes (DEGs). Of these, 157 DEGs were upregulated and 246 DEGs were downregulated. Nine unigenes related to the ubiquitin-proteasome pathway were identified using differential expression analysis. This study initially revealed that the differences in growth of rice flower carp could be due to hypertrophic growth of muscle fibers caused by higher protein deposition, and the ubiquitin-proteasome pathway was an important factor affecting the growth rate of rice flower carp. E3 ubiquitin-protein ligase ari7, g2e3, Neurl1 and rnf144ab were upregulated in the slow-growing fish, indicating the binding of ubiquitin to target protein was enhanced. Foxo3 was upregulated in the slow-growing fish, which could promote the muscle loss. Eif4a2 was upregulated in the fast-growing fish, increasing protein translation efficiency. Some genes related to active muscle contraction such as actb, actg, camk2a, and camk2b were upregulated in the fast-growing rice flower carp muscle. In summary, these results provide valuable information about the key genes for use as biomarkers of growth in selective breeding programs for rice flower carp and provide novel insights into the regulatory mechanisms of muscle growth.

Proximate composition, fatty acid profile and total amino acid contents in samples of the European eel (Anguilla anguilla) of different weights

European eel of different sizes were caught in the River Ulla (Galicia, NW Spain) during winter. The proximate composition differed significantly between fish of different sizes. Discriminant canonical analysis was used to identify the components that enable specimens of different weights to be distinguished. Fat content was the most variable parameter and was directly related to the weight of the fish. The fatty acids that greater increased their content during the growth of the eel were linolenic acid, arachidonic acid, eicosatrienoic acid, and tricosanoic acid. The lipid profiles and quality indices of the eels indicated their high nutritional quality. The threonine, lysine, serine, arginine, alanine and proline contents were highest in the smaller eels. The European eel is a source of high-quality protein with a well-balanced amino acid profile. Moreover, the ratio of essential to non-essential amino acids was highest in the larger eels.

ANALYSIS OF TRAILS AREA OF Tilapia (Oreochromis niloticus) ON GILL NET WITH DIFFERENT SHORTENINGS:

Knowledge of fish and fishing gear using fish behavior approaches is done to improve the effectiveness and efficiency of fishing. This study aims to determine the effect of shortening on the position of fish caught in gill nets. This research was carried out by using a flume tank with a size of 500 cm x 120 cm x 120 cm which was divided into 3 parts which were limited by waring insulation from polyethylene and nets made from PA monofilament material with treatment on shortening and hanging ratios namely using 40% and 60% shortening (hanging ratio 60% and 40%). Tilapia used in this experiment as many as 74 tails that have been measured are then placed in a maintenance tank. The experiment was carried out in 10 replications in each treatment (shortening and hanging ratio). The results showed that catching tilapia (Oreocromis niloticus) with 40% and 60% shortening with the same mesh size of 7.62 cm caught fish of different sizes. At 60% shortening fish tend to be caught gilled and have a larger size compared to fish caught on 40% shortening which ranges from 21 cm - 23.5 cm while on shortening 40% fish tend to be caught wedged and have sizes ranging from 19.10 cm - 21 cm. Percentage of bondage area to total length of tilapia on shortening was 40% greater, ranging from 4.10% - 7.14% compared to 60% shortening which ranged from 2.29% -3.48%.

Karakteristik Sensoris Ikan Lele Sangkuriang (Clarias gariepinus) Berbumbu dengan Perbedaan Teknik Budidaya dan Ukuran Ikan

This research aims to determine preference level for catfish (Clarias gariepinus) spiced with differences technique in organic Aquaculture and non-organic Aquaculture as well as differences in fish size. This research treatment used the method of aquaculture and difference in the size of fish. Aquaculture method (A) namely A1= Conventional and A2= Organic while the second treatment was the difference in the weight of fish (B) namely B1= 100 g, B2= 200 g and B3= 300 g. The spiced catfish was cooked by way of deep-fried Further sensory testing. The method used in this research was the method of experimentation and statistical analysis used the Friedman Conover test. The results indicated that fish had the best texture, aroma and taste in the A2B1 treatment.

Length-weight relationship, morphometric characters, and meristic counts of the coldwater fish Crossocheilus diplochilus (Heckel) from Dal Lake

Abstract Morphometric and meristic characters are very important for the identification of any fish specimen. The present study aims to describe the morphometric and meristic characters of the indigenous fish Crossocheilus diplochilus (Heckel) from Dal Lake. This fish is commonly known as Kashmir latia and is called tether locally. In the present study, the material analyzed was 70 specimens ranging in size from 6.9–13 cm (TL) with a mean length of 10.8 cm and a weight range of 3.2–24.0 g with a mean weight of 10.1 g. The parameters with the highest correlations with total length were standard length and fork length at 0.983 and 0.989, respectively. Correlation analysis showed that all morphometric characters changed proportionally as total length increased. The meristic counts analyzed in the present study remained constant in fish of different sizes indicating that they are independent of body size. The study of morphometric characters is very important to determine the growth rate of these fish, which, in turn, is required to properly manage its populations.

Changes in the body chemical composition and the excretion of nitrogen and phosphorus during long-term starvation of Antarctic fish Notothenia coriiceps and Notothenia rossii

This study examined the effect- of starvation on the chemical composition (total protein, crude fat, dry matter, ash) and the excretion of nitrogen (N) and phosphorus (P) of the Antarctic fish Notothenia coriiceps and Notothenia rossii. Starvation resulted in a decrease in lipid content in both species. In Notothenia coriiceps the body fat content decreased from 2.3% to 1.88% and in Notothenia rossii from 0.82% to 0.6%. Excretion rates of N and P were highest on the first day of starvation, then gradually decreased. Average excretion rates (in µmol N or P h−1 100 g−1) of ammonium nitrogen, organic nitrogen, reactive phosphorus, and organic phosphorus respectively were higher for N. coriiceps (8.71, 2.93, 1.09, 0.46) than N. rossii (6.28, 4.94, 0.54, 0.13). During starvation, the proportion of TON in the total excreted nitrogen was on average 43.5% for N. rossi and 24.1% for N. coriiceps, and remained at a relatively stable level. The study confirmed the natural adaptation of the studied fish to the long-term lack of food, and that the excreted loads of N and P may be a source of biogens for autotrophs and serve as a chemical signal in trophochemoreception. The inter-species differences in the excretion of N and P could be due to the differences in fish size, gonad stage of maturity, and nutritional preferences.

Migratory Timing and Rates of Chinook Salmon Bound for the Kwethluk and Kisaralik Rivers

Abstract Detailed information regarding migratory behavior (i.e., phenology and rate of travel) of specific Pacific salmon Oncorhynchus spp. substocks can be used to design management strategies focused on protecting substocks from harvest when desired; however, this information is often lacking. The Kwethluk and Kisaralik rivers are two tributaries of the lower Kuskokwim River that originate and flow through the Yukon Delta National Wildlife Refuge in western Alaska. Although these two systems are the primary Chinook Salmon–producing tributaries within the Yukon Delta National Wildlife Refuge, little is known about migratory behavior of Chinook Salmon destined for these rivers. In 2015 and 2016, 119 Chinook Salmon tagged with radio telemetry transmitters entered either the Kwethluk or Kisaralik Rivers and were tracked throughout their migration to their assumed final spawning location using both ground- and aerial-based tracking methods. We compared migration timing and swim speeds between fish bound for these two rivers and between fish of different sizes and compared the consistency among the 2 y. In general, we found that fish bound for the Kwethluk and Kisaralik rivers exhibited similar migration behaviors in 2015 and 2016, including entry timing into the Kuskokwim River and migration rates once in the tributaries. A key finding was that Chinook Salmon swam fastest (range of means between years: 20–45 km/d) in the main-stem Kuskokwim River and slowed significantly (4–15 km/d) upon entry into lower portions of the tributaries. Our findings have relevance for harvest management strategies; for example, temporal fishery closures will impact Chinook Salmon bound for both the Kwethluk and Kisaralik rivers equally given their broad overlap in entry timing, and individuals will remain vulnerable to harvest for longer periods when located in tributaries rather than the portion of the main-stem directly below the tributary confluences.

Effect of three different codend designs on the size selectivity of juvenile cod in the Barents Sea shrimp trawl fishery

Shrimp trawlers often use a Nordmøre sorting grid ahead of a small mesh codend to avoid bycatch of juvenile fish while allowing shrimps to be efficiently caught. However, small fish can pass through the grid to enter the codend and risk being retained. The risk of retention for fish of different sizes depends the size selection in the Nordmøre grid and the size selection in the subsequent codend, which makes the process complex and often results in a bell-shaped size selection curve. In the Barents Sea shrimp fishery, cod (Gadus morhua) is one of the species of concern because of its great commercial value. We studied the size selection of juvenile cod when the trawl was equipped with the compulsory gear in the fishery: a 19 mm Nordmøre grid followed by a 35 mm diamond mesh codend. As expected, the size selection curve showed a bell-shaped signature, with a certain size range of juveniles having high retention risk, while the risk for smaller and bigger cod was smaller. The retention risk was highest for cod between 12 and 20 cm in length. We also tested two alternative designs in the aft section of the gear: a codend with 35 mm square mesh panels and a square mesh sorting cone section. Neither of these designs affected the size selection in the trawl significantly.

Effects of Total Dissolved Gas Supersaturation in Fish of Different Sizes and Species.

Two endemic fish in the upper Yangtze River, the Rock Carp (Procypris rabaudi) and Prenant’s Schizothoracin (Schizothorax prenanti), were used as research objects in this study to assess the effects of total dissolved gas (TDG) supersaturation on fish of varying sizes. Fish were exposed to TDG-supersaturated water at the levels of 145, 140, 135, 130, and 125%. The results showed that fish swam slowly, responded clumsily, and then exhibited spiral swimming performance after a period of exposure to TDG-supersaturated water. Fish exhibited exophthalmos, body swelling, gill bleeding, and caudal fin bleeding when they died in the TDG-supersaturated water. With the increase in TDG supersaturation, the tolerance capacity of fish to supersaturated TDG significantly reduced. At high supersaturation, the difference in survival time between species was not significant, while fish with smaller sizes showed greater tolerance capacity. At low supersaturation, the tolerance capacity of fish was mainly affected by species, and the influence of size was relatively small. With the decrease in TDG supersaturation, the catalase (CAT) activity first increased and then decreased. Rock Carp displayed significantly less activity than Prenant’s Schizothoracin on exposure to TDG-supersaturated water. At high supersaturation levels, the CAT activity of Prenant’s Schizothoracin of small size was greater than that of large Prenant’s Schizothoracin. In contrast, small Prenant’s Schizothoracin showed less CAT activity at low TDG levels than did large individuals.

Evaluation of passage and sorting of adult Pacific salmonids through a novel fish passage technology

Throughout their life cycle, salmonids migrate between different habitats. During their journey, they often encounter barriers, such as hydropower dams, which may impede their migration and therefore decrease habitat connectivity. Fish passage systems have been developed to enable the migration of fish around barriers but their design is rarely adaptable to a wide range of species and hydraulic conditions. The Whooshh Fish Transport System (WFTS) is a fish passage technology that was designed to move fish around barriers through a flexible tube using differential air pressure. In this study, we evaluated the combination of the WFTS with the Whooshh Ellips Scanning Sorting system (WESS). This combined system allows autonomous and volitional entry, and subsequent selective upstream passage for fish of different sizes. The sorting by size and the passage efficiency of Chinook salmon (Oncorhynchus tshawytscha) and steelhead (O. mykiss) through the WESS-WFTS was assessed. We found that the WESS-WFTS was able to sort the fish by size, few fish had external injuries, and few unexpected events (e.g. backward transport, discontinuous transport) occurred. Our results support the use of the WESS-WFTS as an effective transport system for adult salmonids when used in conjunction with a volitional fishway entrance.