Journal of fish biology最新文献

The devil firefish, Pterois miles, an invasive alien species, presents a growing threat to marine biodiversity due to its rapid population expansion and significant ecological impacts in the Eastern Mediterranean Sea. This study, conducted between February 2020 and April 2021, aimed to assess the growth patterns and reproductive behaviour to better understand its invasion dynamics in Turkey. Monthly sampling revealed its length-weight relationship, with positive allometric growth. The reproductive dynamics showed a prolonged spawning season from June to November, with females displaying high fecundity, averaging 20,743 oocytes per batch. Females reached first maturity at 20.1 cm total length, and its natural mortality rate was estimated at 0.8 per year. Understanding life-history characteristics of lionfish is important for understanding its invasion success and may help develop effective measures to control its invasion to protect regional marine native biodiversity.

The European catfish (Silurus glanis) is a giant Eurasian freshwater fish that has become a high-impact invasive species in Western Europe. In Spain, it was first introduced in 1974 in the Ebro River for sport fishing, and has since spread to multiple river basins, despite bans. We compiled all known occurrence records in Spain (1974-2024) from scientific surveys, government databases and citizen science, standardizing them on a 10 × 10 km grid. Using first-detection data per waterbody, we reconstructed the invasion timeline and calculated decadal expansion rates. We then applied nonlinear models to project future spread up to 2030. S. glanis now occupies seven major Iberian basins, expanding from one grid cell in the 1970s to 129 cells by 2024. The invasion was initially slow (1970s-1990s), followed by a rapid expansion from 2000 to 2009, when the area occupied increased six-fold. Since 2010 its expansion has moderated, although new introductions in the Duero, Guadalquivir and Andalusian Mediterranean basins have driven localized explosive growth. Logistic and Gompertz models suggest the invasion may be approaching saturation in long-invaded basins (e.g. Ebro), projecting only a slight increase in total area occupied by 2030. However, model confidence intervals remain broad, reflecting uncertainty due to potential illegal translocations and climate-driven habitat changes in the future. Our findings underscore the urgent need for proactive management: preventing human-mediated jump dispersal, enhancing monitoring for early detection and enforcing regulations. Continued data updates and risk modelling are vital to inform policy and targeted control against this high-risk invader.

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.