This study examined patterns of fish community composition and diversity across five sub-basins of the Nan River basin, northern Thailand, using diversity metrics and multivariate analyses. A total of 5467 individuals representing 109 species, 70 genera, 21 families, and 11 orders were recorded across 47 sampling sites. Fish assemblages exhibited pronounced spatial heterogeneity among sub-basins, with significant differences in species richness, diversity, and taxonomic composition. The ten most abundant species accounted for approximately 81.9
Young-of-the-year spot (Leiostomus xanthurus) intra-annual cohort growth rates are influenced by the timing of their arrival to and environmental conditions within estuaries. Fish growth rates while in estuaries positively affect juvenile emigration to deeper estuarine and offshore habitats as well as the resulting potential year class strength as age 1 subadults. Spot from North Inlet estuary, South Carolina, USA, were collected from an intertidal creek pool biweekly during 2020 to evaluate potential effects of the seasonal arrival timing and water temperature, chlorophyll, and salinity during residency on standard length (mm), biomass (g dry tissue), and related growth rates including the transition from isometric to allometric growth. Representatives from three young-of-the-year spot cohorts (n = 974 fish) entered the estuary during early December 2019 (11–16 °C), early February 2020 (10–14.9 °C), and mid to late April 2020 (20–24.9 °C). Water temperature experienced during intertidal creek use as indicated by degree days positively influenced fish growth in length and biomass for all three 2020 cohorts more strongly than either chlorophyll or salinity. The April cohort increased in length while using the intertidal creek pool at a much faster rate (0.29 mm/d) than the December and February cohorts (0.22 and 0.25 mm/d, respectively). However, the April cohort increased in biomass in the intertidal creek pool more slowly than the other cohorts and generally had lower weights than fishes in the earlier cohorts at the same standard lengths. All cohorts transitioned from isometric to allometric growth between 59 and 61 mm ± 2 mm standard length at 0.44–1.35 g dry tissue weight. The February cohort that arrived in the intertidal creeks just before the spring bloom and moved to deeper habitats in early fall had the largest biomass at the end of intertidal creek residency which might enhance future survival and reproduction success.
Understanding long-term effects from land use and land cover (LULC) on watersheds has been essential for the conservation and management of fishes. Watersheds are a mosaic of different LULC types that produce multiple and interactive effects on fishes. Using a combination of field and geoprocessing methods across spatiotemporal gradients, we investigated the effects of LULC on cold-water, stenothermic fishes in a relatively undisturbed yet dynamic watershed (Caldwell Creek, Pennsylvania, USA). Our goals were to (1) describe how watershed-scale LULC from human activities (agriculture and development) and beaver activity (Castor canadensis; wetlands) have changed over time and (2) use long-term field surveys of fish assemblages and water quality parameters to determine whether those LULC patterns were associated with subsequent changes in fish and water quality. Results show evidence that human LULC activities from development and deforestation have induced watershed-level shifts from cold-water to warm-water assemblages and that cold-water trout densities are highest in watersheds of higher contemporary agriculture. However, there was also evidence that juvenile and adult stenothermic trout responded differently to long-term LULC activities from beavers and humans. Whereas juvenile cold-water trout densities were negatively associated with developed LULC, adult cold-water trout were negatively associated with wetland activity. Taken together, these results reveal the complex historical and contemporary interactions between beavers, humans, and fishes. Our study emphasizes the need for considering multiple LULC drivers in the context of fish conservation, especially in the realm of watershed restoration.
Hypomelanosis, encompassing pigmentary anomalies such as albinism, leucism, and piebaldism, is rare among chondrichthyans and remains poorly understood in terms of its ecological consequences. Here, we provide a global synthesis of hypomelanosis in Chondrichthyes, integrating published and unpublished records. Our dataset comprises 148 cases across 75 species from 38 families, with albinism and leucism being the most frequently reported conditions. The type of hypomelanosis was not significantly associated with sex, maturity stage, or habitat, suggesting a broad but unevenly documented distribution. We also report the first case of piebaldism in the whale shark (Rhincodon typus), characterized by a patchy absence of dermal melanophores while normal iris pigmentation is maintained. By synthesizing taxonomic and geographic information, this study establishes a comprehensive reference for pigmentation anomalies in chondrichthyans, identifies key gaps in current reporting, and outlines implications relevant to future ecological and conservation research.
The spatiotemporal scales at which aquatic species use habitats are a key component of their behavioral ecology and are essential considerations for designing and evaluating management strategies. Here, we assess the behavioral ecology of permit (Trachinotus falcatus) in relation to a newly established seasonal fishing closure (SFC) in the Lower Florida Keys to evaluate its effectiveness for protection. Permit are an important recreational species that are highly mobile and aggregate seasonally to spawn. In 2021, managers implemented a SFC at Western Dry Rocks (WDR) to reduce recreational angling pressure on multiple species during critical spawning periods. Using acoustic telemetry, we quantified permit residency time at WDR and three non-closure reference sites across the Lower and Middle Florida Keys to examine behavioral changes before and after the SFC was established, and across seasonal and lunar patterns. We also evaluated connectivity among sites to assess movement responses. Since the SFC, residency (measured as probability of detection) increased at WDR, and was highest during peak spawning (April–July) and around the full and new moons. Detection probabilities before and after the SFC was established varied at the reference sites, indicating site-specific changes in behaviors. Connectivity remained consistent across all reference sites since the SFC was established, though there was limited connectivity between the Lower and Middle Keys. Our findings suggest that permit showed patterns consistent with a positive behavioral response to WDR SFC, but there is room for spatiotemporal refinement. This study also demonstrated how behavioral metrics derived from acoustic telemetry can be used to assess the performance of protected areas, providing valuable tools for aquatic conservation and management.
