Journal of fish biology最新文献

The diet of indicator fish species plays a crucial role in assessing ecosystem health. This study evaluated streams with and without urban influences, focusing on abiotic parameters and the trophic ecology of Psalidodon fasciatus and Piabina argentea. Forested streams exhibited higher redox potential, dissolved oxygen, transparency, and depth, whereas urban streams had higher temperatures, greater widths, and increased levels of total dissolved solids, conductivity, total coliforms, and thermotolerant coliforms. The P. fasciatus population exhibited isometric growth in forested streams and negative allometric growth in urban streams. Conversely, P. argentea exhibited negative allometric growth in both types of environment. The diets of both species included items of autochthonous and allochthonous origin. P. fasciatus had a similar diet in both stream types, whereas P. argentea's diet varied significantly between forested and urban streams. These findings highlight the importance of understanding the interplay between environmental characteristics and species diets, offering crucial insights into the health status of streams, especially those impacted by urbanization.

Anadromous salmonids migrate seaward to exploit feeding and growth opportunities in marine habitats, yet how smolt biological characteristics influence their marine migratory behavior remains poorly understood. This study used 9 years of trout (Salmo trutta) population monitoring data from 15,595 tagged age-0+ parr, 1033 smolts detected migrating downstream in spring, and 99 adults detected returning from their first marine migration to the River Frome (Dorset, UK) to investigate the influence of smolt biological characteristics on their migration timing and maiden marine sojourn duration. Age-specific differences in the influence of smolt length on migration timing were found, with longer 1-year-old smolts emigrating later than their shorter counterparts within the same age class, but the opposite association existed for 2-year-old smolts. A bespoke integrated statistical model quantified the effects of smolt emigration day of year, age, sex, and length on the probability of first-time migrants returning to the river after one or more sea winters. Younger, later migrating smolts had a longer marine sojourn duration than their older, earlier migrating counterparts, and females remained at sea for longer periods than males. Although the statistical model was designed to maximize the use of information available in the data, it revealed only weak effects of smolt biological characteristics on the maiden marine sojourn duration. A complementary simulation study suggested that detecting more spring migrating smolts and analyzing longer time series of trout population monitoring data would increase the ability to detect statistically significant effects. Therefore, a strategic review of the trout population monitoring program, including more long-term biological data collection, is recommended. The modelling work presented here can provide guidance on the size of the required dataset and how to maximize the power of imperfect data.

The tambaqui (Colossoma macropomum, G. Cuvier 1818) thrives both in the ion-poor waters of the Amazon and in commercial aquaculture. In both, environmental conditions can be harsh due to low ion levels, occasional high salt challenges (in aquaculture), low pH, extreme PO₂ levels (hypoxia and hyperoxia), high PCO₂ levels (hypercapnia), high ammonia levels (in aquaculture), and high and low temperatures. Ion transport across the gill is affected by active transport processes, passive diffusive permeability, ion concentrations (the chemical gradient), and transepithelial potential (TEP, the electrical gradient). The latter is a very important indicator of ionoregulatory status but is rarely measured. Using normoxic, normocapnic, ion-poor, low-dissolved organic carbon (DOC) well water (27°C, pH 7.0) as the acclimation and reference condition, we first confirmed that the strongly negative TEP (-22.3 mV inside relative to the external water) is a simple diffusion potential. We then evaluated the effects on TEP of more complex waters from the Rio Negro (strong hyperpolarization) and Rio Solimões (no significant change). Additionally, we have quantified significant effects of acute, realistic changes in environmental conditions-low pH (depolarization), hypercapnia (depolarization), hypoxia (depolarization), hyperoxia (hyperpolarization), elevated NaCl concentrations (depolarization), and elevated NH₄Cl concentrations (depolarization). The TEP responses help explain many of the changes in net Na⁺ flux rates reported in the literature. We have also shown marked effects of temperature on TEP and unidirectional Na⁺ flux rates (hyperpolarization and decreased fluxes at 21°C, depolarization and increased fluxes at 33°C) with no changes in net Na⁺ flux rates. Calculations based on the Nernst equation demonstrate the importance of the TEP changes in maintaining net Na⁺ balance.

Pacific Island communities are heavily dependent on fisheries for subsistence and livelihoods. Yet, despite their importance, coastal fisheries are poorly managed and commercial pressures increasingly threaten them. Groupers (Epinephelidae) are exceptionally vulnerable to overexploitation due to aspects of their biology while their economic value makes them a prime target for commerce. Fiji has a significant grouper fishery and is a useful case study to assess a data-poor, economically valuable sector to evaluate management measures, options, and needs. Data from multiple sources over three decades were integrated with original research involving fisher interviews, market surveys, stock assessments, and underwater census to assess the status of the country's grouper fishery. Catch rates are declining and trade now includes a high percentage of immature groupers, with aggregating species (mainly Epinephelus polyphekadion, Epinephelus fuscoguttatus, Plectropomus areolatus, Plectropomus leopardus) particularly at risk. Estimated annual grouper landings are increasing and now exceed 1000 mt. There is an urgent need to update Fiji's grouper size limits which are grossly inadequate. To build public support and increase awareness, government and nongovernmental organizations should invest in the national 4FJ Fish Smart campaign. Key management recommendations for groupers are (1) improved spatial and temporal protection of spawning aggregations and (2) increased minimum-size restrictions for capture and sale. Findings apply broadly to valuable and vulnerable coastal fin-fisheries in reef ecosystems across many Pacific Island countries and highlight the importance of using multiple data sources and approaches to understand and manage important data-poor fisheries.

The deep-sea demersal fish fauna is characterized by a prevalence of elongated-body forms with long tapering tails. Using baited camera landers at depths of 4500-6300 m in the Pacific Ocean, we observed multiple instances of backward swimming using reverse undulation of the slender body in four species: the cutthroat eel Ilyophis robinsae, abyssal grenadier Coryphaenoides yaquinae, and cusk-eels Bassozetus sp. and Barathrites iris. Backward swimming was used as an escape or repositioning maneuver, reversing for up to seven tail beats before resuming forward swimming in a new direction. The eel I. robinsae reversed with a swimming wave frequency of 0.51-0.95 Hz, wavelength 0.6-0.75 of the body length (L), and large amplitude movements of the head from side to side. C. yaquinae reversed relatively slowly at 0.21-0.52 Hz and wavelength 0.5-0.7 L aided by propulsive movements of the pectoral fins and minimal lateral movement of the head. The ophidiids also used reversed propulsive body waves augmented by paddling with the pectoral fins but with some lateral movement of the head. Pectoral-fin movements in all species were in synchrony with the body movements. The elongated-body form enables backward swimming by reversal of the anguilliform propulsive wave and has the advantage that the fish automatically returns to safety along the path recently traveled. This maneuverability conferred by an elongated body may be a significant factor in selection for body shape in deep-sea fishes.

Understanding the developmental sequence characteristics of the vertebral and appendicular skeletons of the larvae and juveniles of Larimichthys crocea (Naozhou population) can provide theoretical basis for seedling cultivation, environmental adaptation, and taxonomic identification. The cartilage-bone double staining method was used to stain, observe, and analyse the vertebrae, pectoral fins, anal fins, caudal fins, and dorsal fins of the larvae and juveniles of L. crocea (0-30 days post-hatching [DPH]). Results showed that the notochord of the larvae and juveniles of L. crocea was tubular. At 6 DPH, there was obvious segmentation. At 8 DPH, the neural arches began to differentiate, and at 10 DPH, the haemal arches began to differentiate, with complete segmentation of the notochord. At 14 DPH, the dorsal and ventral ribs became clear, and the neural and haemal spines were completely formed by the elongation of the neural and haemal arches, respectively. At 18 DPH, the vertebral bones began to ossify, and ossification was complete at 28 DPH. The median fins of the larvae and juveniles of L. crocea formed in the order of caudal fin, anal fin, and dorsal fin. Among the 800 L. crocea larvae samples, 248 were observed to have skeletal deformities, with a deformity rate of 31.00%. The spine of L. crocea consists of 26 vertebrae, with developmental abnormalities mainly including vertebral anterior convexity, bifurcation of neural spines, vertebral body fusion, and redundancy of neural spines. The above results provide a theoretical basis for enriching the developmental biology of L. crocea.

Preference tests are commonly used to assess fish behavior and cognition in several research fields. This study aimed to investigate how fish perform in a preference test involving extended habituation to the apparatus, which was expected to reduce stress. We contrasted the choice between a sector of the apparatus with natural vegetation, expected to be the preferred stimulus, and a barren sector. Initially, we demonstrated that guppies' preference for the sector with vegetation increased after a 5-day habituation period (Experiment 1). Subsequent experiments systematically modified the testing paradigm to observe effects on the preference. Experiment 2 introduced a physical separation between sectors to facilitate discrete choices, Experiment 3 tested groups of fish, and Experiment 4 used wild guppies. Only the modification in Experiment 3 impacted preference scores: guppies tested in groups showed a higher preference for the vegetation stimulus and spent less time in the central, no-choice sector of the testing apparatus. Overall, this study supports the importance of methodological details in preference tests and highlights the benefits of extended habituation and group testing. Researchers should consider these factors when designing experiments to evaluate cognitive abilities or behavioral preferences in fish. Tailoring testing paradigms to specific research goals can improve the reliability and comparability of results, contributing to a deeper understanding of fish behavior and welfare.

The roundscale spearfish (Tetrapturus georgii) is a poorly studied species with limited information available on its biology, ecology, and population status. Although the adult life stage of the species is morphologically distinguishable from closely related species such as the overexploited white marlin (Kajikia albida), misidentification is common, adding to the uncertainties connected with population assessments of these pelagic highly migratory species. Although genetic studies have recently confirmed its distinction from congeneric species, much of the reproductive biology and population dynamics of T. georgii remain unknown, underscoring the need for further research to guide conservation and management strategies. This study reports the first documented records of an egg and a juvenile T. georgii. Here, we provide photographs, morphological descriptions, and collection site data for genetically confirmed egg and juvenile specimens obtained during two multipurpose research surveys in the Sargasso Sea Subtropical Convergence Zone. These findings contribute new insights into the reproductive biology, early life stages, and ecology of this elusive species.

This study examined the effect of dietary selenium (Se) fortification on growth efficiency, antioxidant status, and liver gene expression in juvenile pangasius catfish. Sodium selenite was incorporated into a basal diet at incremental levels of 0-2.0 mg Se/kg. This resulted in final Se concentrations of 0.63, 0.85, 1.15, 1.68, 2.10, and 2.65 mg Se/kg, respectively. A total of 15 fish, with an average individual weight of 5.6 ± 0.1 g, were subjected to one of six dietary treatments and fed in triplicate over a 60-day period. A significant dose-related enhancement in growth performance was observed, with the optimal dietary Se requirement estimated at 1.75 mg Se/kg. Se-fortified diet significantly increased the activities of digestive enzymes (lipase and protease) as well as antioxidant enzymes, including catalase, glutathione peroxidase, and superoxide dismutase in the liver. Notably, the group fed 1.68 mg Se/kg displayed the highest levels of these enzymes. Additionally, selenium supplementation resulted in an upregulation of the relative expression of insulin-like growth factor 1X1 and 1X2 in the liver, highlighting its pivotal role in growth regulation. Blood parameters showed significant improvements in mean corpuscular hemoglobin and hemoglobin levels with Se supplementation. Proximate analysis showed increasing Se intake resulted in a significant rise in muscle protein content. In pangasius catfish, our results indicate that dietary selenium supplementation can enhance growth efficiency, antioxidant capacity, and hepatic gene expression.

This study investigates the growth and calcification of the appendicular skeleton in Raja asterias (Delaroche, 1809), a member of the Batoidea, to explore the relationship between histomorphology and the mechanics of batoid locomotion within the water column. Although much prior research has focused on the "tessellated pattern" in these fishes, the variable structure of the appendicular skeleton provides fresh insights into the understudied interplay between skeletal histomorphology and the mechanical functions of Batoidea fins. The shape and initial growth of fin cartilage are influenced by the orientation of chondrocyte mitoses prior to mineral deposition, with subsequent calcification playing a pivotal role in shaping skeletal architecture. This study documents two distinct growth patterns: "crustal" and "catenated." The crustal pattern is predominantly observed in larger skeletal elements, such as the central body structures (skull, rostrum, and jaws), girdles, pterygia, and compound radials, whereas fin radials follow the catenated growth pattern. Notably, early-stage chondrichthyan cartilage shares similarities with mammalian metaphyseal growth plate cartilage, though in chondrichthyans, the calcified matrix is not resorbed or replaced by bone. Additionally, a previously unrecognized calcification pattern is identified in the pelvic-fin radials of R. asterias, indicating that the mechanical demands of locomotion in the water column may have driven the evolution of variable fin flexibility in Batoidea. This flexibility is achieved through joint mobility (diarthroses and amphiarthroses), specialized fin structures, and the distinct calcification patterns of the pectoral and pelvic fins.