Journal of fish biology最新文献

Syngnathidae are a charismatic family of teleost fishes, represented by seahorses, seadragons, and pipefishes. Syngnathidae are mainly composed of marine species, but about 30 species of pipefishes inhabit freshwater insular environments of the Indo-Pacific realm. Recent research has shown that some freshwater pipefish species are amphidromous and exhibit high intraspecific divergences across their distribution range, like Microphis brachyurus (Bleeker, 1854) distributed from Sri Lanka to French Polynesia and Microphis retzii (Bleeker, 1856) distributed from Taiwan to Indonesia. In this study, we used the mitochondrial cytochrome oxidase I (COI) partial gene of 91 specimens of M. brachyurus and 30 specimens of M. retzii from localities representative of their respective distribution area to improve knowledge on the population structure of these two widespread species. Genetic species delimitation and phylogeographic analyses were combined to explore spatial patterns of genetic diversity across the distribution ranges of the two species. We have highlighted deep genetic structuring within the two species and relate these results to various biotic and abiotic factors. For M. brachyurus, the population in Polynesia is distinct from those in the West Pacific, suggesting its distinctiveness and recognition as an evolutionary significant unit (ESU). For M. retzii, three lineages are delimited in its range distribution, suggesting the existence of two distinct species in Southeast Asia (Bali/Java/Lombok and China/Taiwan). Pipefish species are particularly vulnerable to anthropogenic pressures (inherent to Syngnathidae and insular environments). The present results, revising species delimitation and geographic distribution, will help implement effective conservation and management measures.

Recent research has looked at various macroalgae species as dietary components or feed additives for a variety of fish species due to their nutritional value. The objective of this study was to examine the impact of Najas indica, a macroalgae extract, on the growth performance, proximate composition, and metabolic activities of monosex tilapia (Oreochromis niloticus), while also isolating the compounds present. Three distinct solvents (n-hexane, ethyl acetate, and ethanol) were used to extract bioactive compounds from a coarse powder of macroalgae after drying and grinding, and gas chromatography-mass spectrometry (GC-MS) analysis was used to detect bioactive compounds. The extracts were combined with commercial feed (0.4%) and applied to the treatment with three replications and a control containing 50 fingerlings per tank for 5 weeks. The findings indicated a significant increase in the final weight, weight gain, specific growth rate (SGR), and survival rate among the treated fish, whereas the feed conversion ratio (FCR) was observed to decrease in comparison to the control group. Significantly higher levels of protein and lipids were found in treated fish, whereas moisture and ash levels were significantly lower compared to control fish. In treated fish, the digestive enzyme amylase was significantly higher, but the protease enzyme reduced significantly. The antioxidant enzyme superoxide dismutase activity (SOD) was significantly higher in the treatment group, whereas the catalase (CAT) enzyme did not differ significantly. A total of 47 bioactive compounds were identified in N. indica, among which the prominent compounds included n-hexadecanoic acid, neophytadiene, phytyl palmitate, d-mannitol, and heptanoic acid. The results obtained from this study indicate that the utilization of N. indica macroalgae extract has the potential to serve as an additional dietary component, therefore, enhancing the growth performance and metabolic functions of fish.

In the context of global change, reviewing the relationships between marine fish traits and their range shifts is required to (1) identify ecological generalizations regarding the influence of traits on range shifts at a global scale and (2) investigate the rationale behind trait inclusion in models describing those relationships. We systematically searched for studies on marine fish assemblages that identified distributional shifts and analyzed the relationship between fish traits and these shifts. We reviewed 29 papers and identified 11 shift type characterizations and 41 traits, noting significant variation in measurement methods and model types used to describe their relationships. We identified global trait redundancies in the relationship between fish traits and latitudinal range shifts. These trends are related to the fishes' latitudinal range, trophic level, water column habitat, body size, size-at-settlement, growth rate, and larval swimming ability. The first four traits, along with fish bottom habitat, biogeographic affinity, diet, and thermal affinity, also showed significant relationships across four ways to characterize horizontal range shifts of fish species. The significance of these traits suggests their relevance in range shifting, regardless of the analyses conducted, biogeographic realm, and range shift type. However, trait redundancies require further consideration, mainly because some traits show opposing relationships in different studies, and important biogeographic research gaps limit global generalizations about the trait-range shift relationship. Half of the studies analyzed provided a rationale for 23 out of 41 traits. We also provide guidelines for future work to better understand the influence of traits on fish range shifts.

Silky shark (Carcharhinus falciformis) populations in the South Atlantic Ocean are listed as vulnerable under the IUCN. In fact, this species is classified as critically endangered in Brazil under the Ministry of the Environment. The present study reports the first opportunistic sighting of an aggregation of 250-300 silky sharks in the Alcatrazes Archipelago Wildlife Refuge. Aggregation sites are important in the life cycle of silky sharks, and identifying these sites is essential for conservation efforts.

This study examines the physicochemical characteristics, morphometric features, biometric growth parameters, biological indices, physiological parameters, and biochemical profiles of Schizothorax niger population. The physicochemical analysis revealed a maximum temperature of 12.93 ± 1.33°C and hardness of 156.53 ± 12.82 mg/L in Dal Lake, whereas the Jhelum River had a minimum level of 10.94 ± 1.12°C temperature and 128.31 ± 11.62 mg/L of hardness. Dal Lake had a neutral pH (7.5 ± 0.2) and lower dissolved oxygen (6.8 ± 0.4 mg/L) compared to the Jhelum River (pH 7.2 ± 0.3; dissolved oxygen 7.5 ± 0.5 mg/L). Morphometric analysis showed significant differences (p < 0.05) in fish length (Dal Lake: 18.4 ± 2.1 cm; the Jhelum River: 21.0 ± 1.8 cm) and weight (Dal Lake: 74.5 ± 9.8 g; the Jhelum River: 92.2 ± 7.4 g) between the sites. Biometric growth parameters demonstrated a positive allometric growth pattern, with Dal Lake having a steeper slope (b = 3.15) than the Jhelum River (b = 2.98). Biological indices revealed gender-based variations in the gonado-somatic index (GSI) and hepato-somatic index (HSI), with GSI being higher in Dal Lake (0.21 ± 0.02) and HSI in the Jhelum River (1.04 ± 0.09). Haematological and biochemical analyses showed significant differences in parameters such as haematocrit (Dal Lake: 29.2 ± 2.1%; the Jhelum River: 32.4 ± 1.8%), glucose (Dal Lake: 85.3 ± 5.4 mg/dL; the Jhelum River: 68.1 ± 4.2 mg/dL), and total protein (Dal Lake: 6.2 ± 0.4 g/dL; the Jhelum River: 5.8 ± 0.3 g/dL) between sites. These findings provide valuable insights into the physiological traits and population dynamics of S. niger, informing species-specific conservation strategies and ecosystem management practices.

The central opioid system and dopaminergic activity in mammals play key roles in mediating social reward, impulsivity, cognition, decision making, and motivation for learning and social interactions. Repeated positive fighting experiences enhance the gene expression levels of μ-type opioid receptor (Mor), tyrosine hydroxylase (Th), an enzyme involved in dopamine synthesis, and dopamine receptor type 2 (D2r) in the reward-related brain regions of aggressive mice. However, it remains unclear whether the opioid system and dopaminergic activity are associated with repeated winning in fish. In this study, we investigated changes in the expression levels of Mor, Th1, and D2r in different regions of the brain of adult medaka Oryzias latipes males after intermittent and continuous fight for 3 days. When a pair of males was provided a fighting opportunity for 20 min per day, we noted that within the 3-day observation period, aggressive winning males showed significantly higher expression levels of Mor in telencephalon and diencephalon, Th1 in diencephalon, and D2r in telencephalon than subordinate losing males. However, no such differences in gene expression level were observed between winning and losing males in the 3-day continuous fight. Further, no differences were detected in the total number of aggressive actions among the winners from each fighting test. However, the total number of "chase" actions, with a stronger aggressiveness index, was higher for the repeated winning male in the three-time intermittent fight than for the winner in the 3-day continuous fight. These findings suggest that repeated intermittent winning experiences with strong aggressiveness could be perceived as a reward by O. latipes males.

Salmonid fishes are a widespread and economically important group of fishes that are strongly affected by anthropogenic environmental degradation. Consequently, studies on their behavior and ecology are essential for their conservation. Wild Arctic grayling (Thymallus arcticus) were observed in an unimpacted Alaskan river using underwater video observations for two consecutive summers (2015 and 2016). Foraging, aggressive behavior, and position held by individual fish were quantified. Fish held focal positions in the water column most of the time (mean = 81%), active foraging was observed for 14% of the observation periods, and antagonistic interactions occurred during 5% of the time. The analysis of intraspecific aggression revealed that aggressive interactions occurred between conspecifics of similar sizes (±100 mm), although the winners of bouts were significantly larger than the losers. Notably, initiators emerged as more successful in these bouts compared to receivers, irrespective of body length. These findings underscore the significance of conducting field studies to gain valuable insights into the behavior of fish in their natural stream environments.

Atlantic salmon Salmo salar typically enter fresh water several months prior to spawning and just as pools can provide areas of refuge in river systems, lakes may also provide important refuge habitat during the spawning migration. Using acoustic telemetry we examined the spatial and temporal movements of wild and a ranched strain of Atlantic salmon in a freshwater lake where the main spawning areas were located upstream of the lake. Over the study period (2011-2014), returning adult wild salmon spent an average of 228 days in fresh water and 90% of that time in the lake. On entering the lake, most wild salmon moved quickly to the northern part of the lake, close to the main inflow, spending an average 76% of the time in this location. The average number of days wild fish were absent from the lake during the main spawning period varied between years, ranging from 10 to 26 days for females and 32 to 35 days for males. Seventy four per cent (17/23) of salmon spawners returned to the lake and two salmon subsequently died in the lake post-spawning. Atypically, two salmon were resident in the lake for the whole period in 2013/14. During the study, wild salmon were detected at depths within the top 5 m for 73% of the time. Median depths post-spawning were greater than in the pre-spawning period, when salmon were found to spend extensive periods at depths in excess of 10 m. In July 2013, when the lake was stratified, thermal regulation behaviour was observed in wild salmon, whereby salmon moved to cooler deeper water when water temperatures at 1 m exceeded 20°C. In contrast to wild salmon, the majority of ranch salmon returned to the traps downstream of the lake prior to the spawning period, which would be expected as they were released as smolts below the freshwater lake. Ranch fish spent an average 80% of the time in the vicinity of receivers in the south of the lake and an average 98% of the time within the top 5 m. However, two ranch females were resident in the lake until the following spring and one ranch female moved upstream into the river during the spawning period. Clearly, in this catchment the lake provides an important habitat for migrating adult salmon. In the context of climate change, where thermal and hydrological regimes in rivers are expected to change in response to changes in air temperature and precipitation patterns, the availability of deep lakes that stratify in the summer and cool water refuges in river systems is likely to play a key role in the sustenance and conservation of salmonid species. Information about the migration patterns of Atlantic salmon in undisturbed freshwater systems may also assist in resolving issues associated with fish passage in impacted rivers and inform management decisions.

The magnificent catshark Proscyllium magnificum was described in 2004 based off five specimens collected in the Andaman Sea off Myanmar. It was originally allocated to the genus Proscyllium, but recent molecular analyses suggested it was more closely related to the harlequin catshark Ctenacis fehlmanni from the western Indian Ocean. This study incorporated meristics and external and internal morphology, together with molecular data to reclassify the magnificent catshark as Ctenacis magnificum and provides revised diagnoses for the genera Ctenacis and Proscyllium. Ctenacis consists of two allopatric Indian Ocean species, while Proscyllium is monotypic genus confined to the northwest Pacific. The revised Ctenacis can be distinguished from Proscyllium in having a broader and longer head (head length 21%-23% vs. 16%-18% of total length), distance between pectoral and pelvic bases shorter than head length (vs. greater than head length), more teeth (upper jaw with 80-86 vs. 46-62 tooth files), and a complex colour pattern of dark reddish-brown blotches and saddles (vs. colour pattern of small black spots). A revised key to the genera of proscylliids and species of Ctenacis is provided.

Larval and transforming stages of smallscale weakfish Cynoscion microlepidotus (Sciaenidae) are described and illustrated based on samples obtained in three different sites along the Brazilian coast: São Marcos Bay (Maranhão state), Camamu Bay (Bahia state), and the Cananéia-Iguape Estuarine System (São Paulo state). Identification of early stages of C. microlepidotus was based on meristic counts, such as number of myomeres (22), number of fin spines and rays (dorsal XI, 24, anal II, 9 and pectoral 19), morphological features (presence of supraoccipital crest in larvae from flexion to transformation stages, branched anal fin spines) and pigmentation pattern. Early stages of this species are likely to be confused with Carangidae and Scorpaenidae due to the presence of a supraoccipital crest, and with the Sciaenidae species Stellifer rastrifer, Macrodon atricauda, M. ancylodon, and Isopistus parvipinnis due to branched anal fin elements. However, a distinction can be made when analyzing the set of characters (morphology, morphometry, pigmentation) in relation to the different stages of development.