Journal of fish biology最新文献

Juvenile fish play a crucial role in the health of aquatic ecosystems, serving both as the foundation for future adult populations and as a valuable food source. Studying the juvenile life stage of fish using acoustic telemetry is inherently challenging due to their small size and associated difficulties in tracking and data collection. Recent advances in telemetry, including the miniaturization of tags, have enabled researchers to investigate previously understudied size classes of fish. Tagging fish can introduce sublethal effects that alter their physiology and behaviour, ultimately biasing the collected data; this effect is exacerbated in smaller-bodied fish, which are generally more sensitive to tagging procedures. Our study tested whether tagging juvenile brook trout (Salvelinus fontinalis) of two size classes (10-12 and 13-16 cm fork length, n = 80) with a LOTEK JSATS PinTag (0.22 g, mean tag burden 1.11% of body mass, range 0.54-2.00%) impacted their oxygen consumption rates ( ${\dot{M}}_{O_2}$ ) over the 2 days following tagging. Handling and tagging caused no mortalities, although we observed a nearly significant effect (p = 0.06) of the experimental group (control, anaesthesia, surgery, tagged) on standard metabolic rate (SMR). This was driven by a 7% decrease in the SMR of the tagged animals, which were significantly different from the control group when compared directly (p = 0.02). This marginal effect in standard metabolic rate, combined with the absence of significant effects on maximum metabolic rate, aerobic scope and post-exercise recovery, suggests that the JSATS PinTag does not impair the aerobic metabolic capacity of fish of this size. Our findings indicate that neither the surgery procedure nor the presence of the tag limit the brook trout's capacity for burst movement, which is highly relevant for predator-evasion responses after release in the wild. In addition, we evaluated wound recovery and suture retention over a 3-week period using either braided or monofilament suture material. While braided sutures caused more immediate irritation and were more prone to fungal growth, their quicker expulsion may reduce long-term discomfort compared to monofilament sutures. Determining the optimal suture type may ultimately depend on study duration and objectives, and longer-term monitoring could clarify which material best supports overall healing.

A recent survey of artisanal and subsistence fishers in Madang, Papua New Guinea, resulted in rediscovery of the sailback houndshark Gogolia filewoodi. The five females and one male G. filewoodi recorded in 2020 and 2022 near the Gogol River mouth are the first verified records of this species since its description from a single specimen in the 1970s. Gogolia is a monotypic triakid genus and thus represents a unique evolutionary lineage not seen anywhere else in the world and could be an important marine biodiversity icon for Papua New Guinea.

Deterioration of water quality, especially low dissolved oxygen, has contributed to outbreaks of streptococcal disease in tilapia. It has been reported that hypoxia increases the mortality of tilapia during Streptococcus agalactiae infection. However, the underlying mechanism of the increased susceptibility of tilapia to S. agalactiae caused by hypoxia remains unknown. In this study, the pathological effects of hypoxia and S. agalactiae co-exposure in the liver of tilapia were investigated using transcriptome and metabolome analyses. When subjected to individual hypoxia or S. agalactiae exposure, the liver of tilapia exhibited significant pathological effects, including vacuolation, severe necrosis, nuclear and cellular polymorphism, hemocyte infiltration/leakage and abundant granular deposits. Moreover, these pathological effects became more severe under hypoxia and S. agalactiae co-exposure. In addition, S. agalactiae exposure increased inflammation-related gene expression, including CC1, CC2, IL-1β, TNFα, but this effect was suppressed by hypoxia. Transcriptomic analysis revealed that carbohydrate, lipid and amino acid metabolic pathways were significantly altered in the hypoxia and S. agalactiae co-exposure group compared to those in the control group. Among these metabolic pathways, only lipid metabolism was obviously altered at the metabolite level, as revealed by metabolomics analysis. Further combined analysis of the transcriptome and metabolome suggested that, in lipid metabolic pathways, glycerophospholipid metabolism should be a key pathway in S. agalactiae-infected tilapia under hypoxic conditions. Taken together, the results of the combined analysis of the global changes in the transcriptome and metabolome of the tilapia liver under hypoxia and S. agalactiae co-exposure revealed important metabolic pathways involved in the pathological process by which hypoxia increases the susceptibility of tilapia to S. agalactiae.

Invasive bighead carp Hypophthalmichthys nobilis have spread throughout the Mississippi River basin, negatively impacting ecosystems. We used a remnant population (32 years after stocking) to better understand H. nobilis. We observed high annual survival (>95%), but growth was relatively slow. Lapilli otolith sections were reliable aging structures but underestimated H. nobilis age by ~10%. Dorsal-fin rays and postcleithra also showed some promise for age interpretation. This study provides information about exceptionally old H. nobilis, with unique survival, growth and habitat conditions that could further inform invasion models.

Alarm substance (AS) is widely used in zebrafish (Danio rerio, Hamilton, 1822) antipredator research to elicit an alarm reaction. This alarm reaction consists of stereotypical behaviours, including freezing, erratic swimming and a tendency to dwell at the bottom of the tank (geotaxis). Because the active compound in AS is known to degrade rapidly, many investigators choose to freeze AS until use, whereas others argue for collecting AS freshly the morning of an experimental session. As part of efforts to reduce the number of donor fish necessary for an experiment, we sought to investigate whether AS maintained overnight under cold storage could elicit an equivalent alarm response to AS of equivalent dilution collected freshly. Our results indicate that exposure to AS stored overnight at -20°C elicited a diminished alarm response compared to fresh AS of equivalent dilution. Although frozen AS may still be sufficient for many studies, our results suggest that AS is most potent when collected fresh the morning of experimentation.

Japanese anchovy (Engraulis japonicus) is a small pelagic fish that is frequently targeted by commercial fisheries. Japanese anchovy plays a crucial role as a vital link between primary and higher-order consumers. The elemental mercury in Japanese anchovy muscles easily bioaccumulates and is transmitted to top predators. We investigated the variation in the diets and mercury accumulation of Japanese anchovy in the high seas of the northwestern Pacific Ocean. We measured the amounts of mercury and fatty acids in the muscles of 149 Japanese anchovy specimens that were obtained from the open seas of the northwestern Pacific Ocean (39°2' N ~ 42°30' N, 154°02' E ~ 161°29' E) between June and July 2021. The results revealed that the monounsaturated fatty acid (MUFA) and polyunsaturated fatty acid (PUFA) contents significantly decreased and then increased with the growth of Japanese anchovy (p < 0.001). The standard ellipse-corrected area (SEAc) calculated from the fatty acid profiles showed a decreasing and subsequently increasing pattern with anchovy growth. Trophic niche overlap reflects the degree of overlap in diet composition among species. Compared to the niche overlap among the 91-105, 106-120 and 121-135 mm groups, the niche overlap of Japanese anchovy between the 121-135 and 136-150 mm groups was lower. This change may indicate a dietary shift in Japanese anchovy with a body length of 120 mm. Mercury levels were positively correlated with C22:6n3, C20:4n6 and C20:1n9 contents and negatively correlated with C16:1n7 contents. We suggest that the proportion of higher-trophic zooplankton in the diet increased with the growth of Japanese anchovy, and that zooplankton was likely an important cause of the increase in mercury levels.

The harvest of animals from the wild is a pervasive selective force, especially in fisheries, where harvesting often targets individuals with specific traits. While most research has focused on large-scale commercial or recreational fisheries, little attention has been paid to artisanal fisheries, particularly those targeting ornamental species. Furthermore, environmental factors such as temperature and oxygen levels influence the behaviour of fishes, such as boldness and sociability, but their role in the harvesting process remains poorly understood. Here, we used underwater video to examine how two ornamental Amazonian fishes, Hemigrammus sp. and Copella nattereri, interact with artisanal trap gear. We quantified the number of passes, inspections, entries and exits using latency to inspect and enter traps as proxies for boldness, and coefficients of dispersion (CDs) to assess sociability and group coordination. We found that the majority of fish that inspected traps did not enter them, and a given trap typically caught one species over the other. Overall, Copella were captured more frequently, but within individual trials there was no statistical difference in catch numbers between species. While both species inspected traps, Hemigrammus exhibited significantly more passes and a higher rate of inspection. Latency to inspect and enter traps did not differ between species but decreased with increasing temperature for both. Hemigrammus also displayed greater group coordination, with higher CD values across behaviours. Notably, temperature had opposing effects on coordination: for Hemigrammus, CD of inspections increased with temperature and CD of exits decreased, whereas for Copella, inspection CD decreased and exit CD increased. These findings reveal that different species interact with fishing gear in behaviourally distinct ways, influenced by environmental conditions. This highlights the potential for selective pressures to vary not only by species, but also with ecological context. Understanding such dynamics is critical for predicting how artisanal fisheries may shape behavioural traits in wild populations.

Vocal signalling is an important mode of communication in fishes. The two species of lionfish in the Pterois complex, the Indo-Pacific lionfish (Pterois volitans) and the red lionfish (Pterois miles), are both known to produce different types of sounds with sonic muscles attached to the swimbladder. However, the specific mechanism and the functions of these vocalisations in these invasive species are still unknown. We used three-dimensional bioimaging to describe the anatomy of the sonic muscles of both species. We further quantified the muscles of P. volitans to specifically explore how muscles developed across ontogeny and to test the hypothesis that sonic muscles would show sexual dimorphism if they were a sexually selected trait. Both P. volitans and P. miles showed a physoclistous swimbladder with a bilaterally symmetric pair of extrinsic sonic swimbladder muscles (ESSMs), which have been suggested to control buoyancy and generate vocalisations. Both species also displayed an additional pair of anterior extrinsic muscles, which projected dorsoventrally from the spinal column and inserted onto the anterior wall of the swimbladder, potentially also having a role in sound production. Both types of sonic muscles were present across ontogeny. Quantification of the posterior belly of the ESSMs in P. volitans showed that both the length and mass of these muscles in both mature and immature individuals increased linearly with body size. There were no ontogenetic or sex differences in sonic muscle investment between individuals. Given the primary function of these muscles is to control the swimbladder for buoyancy, this may constrain the modification of these muscles relative to body size, or they may have no differences in their acoustic function between sexes or across ontogeny.

The shortnose sturgeon (SNS; Acipenser brevirostrum) is a United States federally endangered diadromous species. Although SNS spend much of their time in riverine habitat, inter-river migrations have been documented in northern populations. However, the inter-river migratory behaviour and distance capabilities of southern SNS are poorly understood. In this communication, we describe two SNS that migrated approximately 425 km across the coast, far exceeding the previously reported maximum coastal migration distance for the species. These observations offer critical updates for species descriptions and management regarding the coastal migration ability of SNS.