Journal of fish biology最新文献

Triplophysa nayongensis sp. nov., a new blind stygobitic fish, is described here assisted by voucher specimens collected from an underground cave in Zhangjiawan Town, Nayong County, Bijie City, Guizhou Province, China. This species can be distinguished from all its known congeners, which are cave-restricted, based on morphological (eyes either reduced to discernible black dots or entirely absent; anterior nasal flaps not elongated into barbel-like processes; dorsal-fin origin anterior to pelvic-fin insertions; pectoral-fin tips failing to reach pelvic-fin origins; hindmost parts of pelvic fins extending beyond anus but not reaching anal-fin insertion; colourless body; and distal margin of dorsal fin truncate), geographic (upper basin of the Wujiang River vs. other sites) and phylogenetic (monophyletic with respect to close relatives) evidence. The finding elevates the number of cave-dwelling plateau-loach species from 42 to 43 and expands their spatial range to further upper drainage of the Wujiang River, a primary tributary of the Yangtze River.

Sex is an important driver of variation in behaviour, ecology and physiology. Sex identification in the Critically Endangered European eel (Anguilla anguilla) currently requires fish sacrifice, or the use of morphological differences such as body length, which can be inaccurate in certain habitats and at intermediate body lengths. Non-lethal tools for accurate sex identification in this species are therefore required. Here, we test the efficacy of two minimally invasive methods of sex identification: (1) ultrasonography and (2) molecular markers taken from pectoral fin clips. Both methodologies were applied to riverine European silver eel and compared to histological sex identification. Ultrasonography accurately identified the gonads in female eel, with males identified by the absence of detectable gonadal structures. The level of expression of three molecular markers (dcn, LOC111853410, kera) previously used to identify sex in Japanese eel (Anguilla japonica) were evaluated. There was no significant differential expression of the three molecular markers between sexes, suggesting that these markers cannot be accurately used to identify sex in European eel. Our findings suggest that minimally invasive imaging using ultrasonography can be a reliable tool for identifying sex in early-stage adult migratory European eels, with particular use at intermediate sizes (400-500 mm) and animals in habitats where migration potential is limited and may regularly exceed typical growth sizes. This technique can be highly valuable for studies that address ecological, behavioural, conservation and management issues in this Critically Endangered species.

To investigate the impact of tea polyphenols on the health of Pelteobagrus fulvidraco under ammonia stress, a total of 480 juvenile P. fulvidraco were divided into four groups receiving tea polyphenols supplemented diets at 0 mg kg^-1 (C group), 200 mg kg^-1 (L group), 400 mg kg^-1 (M group) and 600 mg kg^-1 (H group) for 56 days. Ammonia stress was applied from days 28 to 56. The results showed that intestinal histological damage was alleviated in the L and M groups under ammonia stress. In the M group, the levels of total antioxidant capacity and Nrf2, HO-1 and Occludin were the highest. Regarding ferroptosis-related genes, DMT1, FTM and FPN1 exhibited their highest expression in the L group, while TF, TFR1, FTL, SLC7A11 and GPX4 showed their highest expression in the M group. FTH demonstrated its highest expression in the H group. Furthermore, the expression of ACSL4 in the L and M groups was significantly lower than that in the C group. Intestinal microbiome analysis revealed enhanced microbial diversity in the tea polyphenol-added groups, accompanied by reduced relative abundance of dominant phylum Fusobacteriota and genus Cetobacterium compared to the C group. These results suggested that dietary supplementation of 200-400 mg kg^-1 tea polyphenols could alleviate ammonia-induced intestinal ferroptosis and histological damage, as well as protect intestinal health by regulating the compositional structure and diversity of the intestinal microflora. Specifically, the 400 mg kg^-1 dose exerted the most comprehensive protective effects. This study provides mechanistic insights into the development of tea polyphenol-based anti-ammonia feed additives for P. fulvidraco aquaculture.

A new labeonin fish, Tariqilabeo kaladanensis, is described from the Kaladan River of Mizoram, northeast India. The new species is distinguished from its congeners by having combination of the following characteristics: frenum of rostral cap exposed, folded and continuous with the subtoral fold, frenum of upper lip covered by the rostral cap, presence of dark humeral spot covering 4th and 5th lateral-line scales extending to scales immediately above and below lateral-line scales, 32-34 lateral-line scales, lacking mid-lateral stripe on the flank and possessing 28-29 gill rakers on the first-gill arch. The morphological distinction of the new species is well supported by the mitochondrial gene data with a wide genetic distance of 4.1%-12.7% (coi) and 7.2%-15.6% (cytb) from all other congeners.

The objective was to estimate the movements and survival of Atlantic salmon smolts migrating downstream through a river-lake system consisting of two large, interconnected lakes (areas 58.2 and 13.2 km², minimum crossing distance 29 and 16 km). Whereas downstream migration in running waters is much studied, limited research in small lakes and reservoirs suggests that smolt survival may be lower when moving through still water. Across two migration seasons, wild and hatchery-reared Atlantic salmon smolts were radio tagged and released in the inflowing river upstream the lake. Tracking of smolt individuals indicated major losses during lake migration. Among 300 radio-tagged smolts, about 90% or more perished during lake migration with loss rates about 3%-4% per kilometre. Migration time through the lakes varied considerably by smolt individual. We conclude that Atlantic salmon downstream migration through lakes may represent major population sinks, on a scale similar to marine losses, but likely depending on exposure (travel distance, time, navigational complexity) and predation risk. This additional cost for salmon populations upstream of lakes makes them more vulnerable and less resilient to environmental stressors. They therefore require special management attention.

Four new species of the small-sized armoured catfish genus Pareiorhina are described from mountain ranges in the Grande River drainage, upper Paraná River basin, based on morphological and molecular species delimitation methods. Molecular analyses based on the cytochrome oxidase subunit I (COI) marker recovered Pareiorhina as polyphyletic, with none of the 11 nominal species, including the 4 newly described, forming a clade with the type species Pareiorhina rudolphi. Instead, two sister clades were recovered outside P. rudolphi: one comprising species with a postdorsal ridge and unicuspid teeth, and another lacking the ridge and bearing bicuspid teeth. The four new species resemble Pareiorhina carrancas and Pareiorhina hyptiorhachis, both readily distinguished by the presence of a postdorsal ridge and simple teeth, and differ from all congeners by unique combinations of body colouration, abdominal plating, vertebral counts, pelvic girdle morphology and morphometric traits. These results underscore the underestimated diversity of the upper Paraná River basin and reinforce the need for continued ichthyofaunal surveys. Furthermore, they highlight the importance of integrating morphological and molecular data to unravel species diversity and distribution patterns of small-sized fish species inhabiting southeastern Brazilian headwaters.

The migratory behaviour of Atlantic salmon kelts is poorly understood. Due to the Atlantic salmon's considerable socio-economic and ecological importance, their precipitous population abundance declines, and the population resilience potential of salmon kelts, addressing these knowledge gaps is important. In this study, directional swimming behaviours and position choice were quantified for the swimming trajectories of 48 acoustically tagged kelts in a regulated river. The kelts exhibited positive rheotaxis under high flow velocities, though their response to turbulence was more varied. The kelts exhibited clear preferences for moving between positions with similar hydraulic conditions and avoided moving to positions where the flow velocity or turbulence changed rapidly. The extent to which the kelts avoided moving to positions with rapid changes in hydraulic conditions varied by individual experience, individual body size, how active the individual was during daytime and how often an individual was detected near a conspecific. This study is the first to combine data on intrinsic individual characteristics with extrinsic hydraulic factors to conduct a detailed analysis of kelt behaviour during migration in a regulated river. By examining these behaviours across different hydraulic conditions, our findings bear important implications for both hydropower development and river management practices.

Pink salmon originate from the North Pacific area but were introduced into northwest Russia from the late 1950s onwards. Since 2017, the alien species has increased dramatically in abundance and rapidly invaded adjacent areas of the North Atlantic region. In the large Teno River in northernmost Norway and Finland, running to the Barents Sea, various monitoring methods originally designed for assessment of Atlantic salmon populations have been used to observe the development in abundance and distribution of pink salmon in the main stem and in a number of tributaries. In addition, environmental DNA (eDNA) sampling has enabled monitoring of these trends across an even wider set of tributaries. The first observations of pink salmon were made in the 1960s, and variable but mostly low catches were recorded in the following decades. In recent years, the total number of pink salmon entering the Teno system increased rapidly from c. 5000 in 2017 to c. 180,000 in 2023. Initially, the invading pink salmon were occupying the main stem, large tributaries and headwater rivers of the catchment, even up to a distance of 250-350 km from the sea. However, in recent years, a greater number of smaller tributaries have been occupied as demonstrated by eDNA detections and other observations. The largest spawning aggregations of pink salmon have been observed in the main stem of the Teno River. Future development in the abundance and dispersal of pink salmon in the Teno system depends strongly on the extent and success of the mitigation efforts in intercepting and removing pink salmon by a weir and trap close to the estuary.

Migrating silver European eels Anguilla anguilla are reported from the inland waters of the island of Cyprus for the first time, expanding the known geographic range in the Eastern Mediterranean of emigrating adults of this critically endangered, catadromous species. Silver eels were captured attempting to migrate to sea from two separate locations. This is important, as Cyprus was previously exempt from European eel management plans due to a presumed absence of significant eel populations, especially of the silver life stage. This now requires urgent review to ensure these populations are managed appropriately.

Intensive multigenerational size-selective mortality has been found to alter collective properties like shoaling via evolutionary adaptations of individual-level behavioural traits. For example, experimental populations of zebrafish (Danio rerio) experiencing intensive large size-selective mortality over multiple generations developed less cohesive shoaling in the laboratory, presumably because these fish were more attentive to environmental rather than social cues. By contrast, zebrafish exposed to small size-selective mortality evolved increased group cohesion. However, these studies were conducted in the absence of explicit predation risk by a live predator. In this study, we examined if size-selective mortality led to divergent responses in shoaling behaviour in the same zebrafish selection lines in the presence and absence of a live predator. The large line generated via size-selective harvest of smaller fish over five generations formed significantly more cohesive shoals than the control line, independent of whether a live predator was present or not. By contrast, the small line generated by size-selective mortality of large fish over five generations did not differ from controls in their shoaling behaviour in the presence or absence of a live predator. All zebrafish groups generally formed more cohesive shoals in the presence of a predator and became more dispersive over a 2-week experimental period. We conclude that the systematic removal of smallest individuals, thereby saving the largest fish from harvest, evolutionarily fosters increased group cohesiveness. These evolutionary adaptations might affect natural predation mortality and catchability by fishing gears.