Environmental Biology of Fishes最新文献

Recruitment is the addition of individuals to a population that generally occurs in the early juvenile phase, which is key to understanding the dynamics of reef fish communities. Through visual censuses in three climatic seasons (dry, rainy, and northerly winds) between 2017 and 2020, the analysis of seasonal and interannual variations in the abundance of fish recruits in a reef lagoon (Mahahual, Quintana Roo, México) was carried out. Temporality was analyzed using average recruit density graphs and multivariate analyses (multivariate ANOVA, ANOSIM, and RDA) to assess composition differences between year and season levels. A total of 9326 recruits were registered, belonging to 36 species and 8 fish families. The Labridae had the greatest number of recruits, followed by Pomacentridae and Scaridae. The recruits were more abundant in the dry season when the average temperatures were 27.50–27.87 °C; meanwhile, they presented a lower abundance in the northerly wind season when the temperature was lower (26.7 °C). The most abundant species was Thalassoma bifasciatum (138.72 recruits/100 m²), followed by Abudefduf saxatilis (100.05 recruits/100 m²) and Halichoeres bivittatus (45.94 recruits/100 m²). The multifactorial ANOVA for the average density and the ANOSIM for the composition of recruits did not show significant differences for the year factor, but they did for the season factor. RDA indicated that the greatest average dissimilarity existed between the dry season and the other two climatic seasons. The results of this study highlight the importance of recruitment during the warm months and the refuge offered by the lagoon for the maintenance of reef fish populations.

The bristlenose pleco (Ancistrus cirrhosus) is a species of Loricariidae armored catfish that breathes air using its highly vascularized stomach when faced with hypoxic aquatic environments. The main goals of this study were to determine the developmental onset of air breathing and air-breathing behavior in A. cirrhosus from juveniles to adults. Developing juveniles reach functional maturity within 4 to 6 months of hatching, growing to an adult length of 8 to 10 cm. To examine the timing of the developmental onset of air breathing, we tested for air-breathing behavior in juveniles beginning at 1 cm in length up through adults at 8 cm in length by exposing each fish to an acute gradual decrease in aquatic oxygen content from 100% air saturation down to 8% air saturation over a 50-min period. Juvenile fish first began to breathe air at body lengths between 2.1 and 3 cm and masses of 1.1 and 2 g. Fish with body lengths above 3 cm all breathed air when hypoxia challenged. In fish that breathed air, there was a weak negative correlation between fish length and % air saturation at which air breathing began. Fish were also exposed to an acute bout of 15% air saturation for 60 min, and breathing behavior was observed. Fish exposed to 60 min acute 15% air saturation exhibited a negative correlation between the frequency of air breathing and fish length. The developing A. cirrhosus can take advantage of the aerial environment once they reach 3 cm in length and 2 g when exposed to aquatic hypoxia. Prior to this size, these animals would potentially succumb to severe aquatic hypoxia without the ability to breathe air.

At the end of the Inuit summer, anadromous Arctic char (Salvelinus alpinus) migrate toward Tasirjuarusik Lake (Kangirsuk, Nunavik, Quebec). They sustain subsistence fishing during the upstream migration. However, during the winter, local Inuit fishers have been unsuccessful in catching Arctic char in this lake, but catches do resume in late spring. The Kangirsuk hunters and fishers’ association, Uumajulirijikkut Kangirsumi, initiated a telemetry study to assess (1) if the Arctic char were overwintering in the lake and (2) if the fish behavior during winter and spring was linked to environmental characteristics (temperature, oxygen, or ice). Eight Arctic char were tagged with acoustic transmitters during their upstream migration, and passive receivers were deployed throughout the lake continuously for 2 years. Five of the tagged fish overwintered in the lake, where they remained inactive for approximately 8 months. The difficulty of catching them in winter is likely due to their low activity level combined with the large areas of littoral zones (selected habitat) in this lake. A significant increase in the activity level of the tagged Arctic char occurred simultaneously with the onset of snowmelt runoff until the complete mixing of the lake. Char left the lake at peak discharge, coinciding with the ice breakup at the lake outlet. The results of this collaborative research, led by the community with locally grounded questions, align with and complement the observations of fishers. Despite the limited number of tagged fish due to community concerns about animal well-being, the results illustrate different migration patterns within this population and shed light on the environmental triggers that lead to the resumption of char activity in spring.

Due to disturbance-driven phase shifts on coral reefs, sponges are an increasingly important microhabitat for reef-dwelling organisms, particularly throughout the Caribbean. The abundance of sponge-dwelling species is expected to be heavily influenced by their degree of habitat specialization, as well as the distribution and morphology of potential host sponges. We conducted surveys along the fringing reefs of Curaçao to test how host sponge community composition and morphology drive occupancy patterns of the yellowline goby (Elacatinus horsti). The assemblage of goby-occupied sponges varied across the island, representing habitat heterogeneity across surveyed sites. We found E. horsti to be a sponge generalist, commonly occupying three species: Aplysina lacunosa, Aplysina archeri, and Neofibularia nolitangere, though all host species had some unoccupied sponges. A variable related to overall sponge size—maximum sponge height—significantly influenced the likelihood of goby occupancy. Goby group size in a sponge was also influenced by maximum sponge height along with the number of oscula and the species of host sponge. Specifically, group sizes were bigger in larger sponges with more openings, and the noxious sponge N. nolitangere hosted groups that were estimated to be 2.6–9.0 times larger than groups in other sponges when accounting for host morphology. Therefore, for these site-attached fish, the opportunity for conspecific interactions varies across different hosts. Collectively, our findings lay the groundwork for future investigations into the ecological trade-offs and fitness consequences of occupying distinct host species and examining the nature of fish-sponge symbioses.

Smallmouth buffalo (Ictiobus bubalus Rafinesque) are a large-bodied fish highly valued and commercially exploited across most of their range. Despite this, relatively little is known of their population demographics compared to other exploited species. To fill these knowledge gaps, we analyzed two independent long-term datasets (30 and 57 years, respectively) and population demographic data (age structure, growth, mortality, age at maturity, and recruitment) from multiple pools of the Upper Mississippi River System (UMRS) and Illinois River (Illinois, USA). Long-term data (30-year dataset) generally show downward trends or significant declines in catch per unit effort in the UMRS, while the 57-year dataset shows a stable trend or a significant increase in the Illinois River. The oldest smallmouth buffalo were estimated to be 39 years old, with nearly every pool sampled having individuals estimated to exceed 30 years of age. Except for Pool 13 of the UMRS, 90% of smallmouth buffalo were estimated to mature between 411 and 470 mm in length or between 8.7 and 11.2 years old. Recruitment was variable: strong year classes were generally preceded by multiple years of weak year classes. Our results indicate that the smallmouth buffalo population may be stable in portions of the UMRS and Illinois River systems, but significant declines in the northern extent of the UMRS may warrant conservation concern. Recent research into ages of buffalofishes shows that consideration should be given to the idea that the UMRS population could be age truncated. Results also emphasize the importance of long-term data and the ability to show changes in exploited populations over time.

Carbon (δ¹³C) and nitrogen (δ¹⁵N) stable isotopes (SI) serve as natural markers for evaluating fish food sources. However, interpreting SI isotope values in newly hatched fish becomes intricate due to the transfer of maternal resources during early development (egg, larvae). This research investigates maternal influences on neotropical freshwater fish larvae growth through SI analysis, focusing on the pacú fish (Piaractus mesopotamicus). The study utilizes a commercial inert feed to assess carbon and nitrogen contributions to larval tissue growth while evaluating the turnover rate, providing valuable insights into early-life nutritional dynamics. Both SI exhibit variations during larval development, following a chronological pattern corresponding to ontogeny, with a significant shift at 13 days after hatching (DAH). Maternal transmission significantly influences isotopic signatures in early larval stages, showing linear correlations between isotopic ratios and standard length (SL) until 15 DAH. C:N ratios decrease from 6.3 ± 0.1 at 0 DAH to 4.2 ± 0.1 at 13 DAH. The isotopic composition of maternal origin aligns with egg stage values, emphasizing the stability of maternal transmission. Under experimental conditions, elemental carbon half-life in tissue (t₅₀) is 6.44 days, and nitrogen t₅₀ is 3.82 days. Maternal isotopic ratios in initial larval development stages offer a potential method for estimating nutritional tracers in field-collected eggs, contributing to understanding the role of freshwater nurseries in comprehending migratory routes, critical hatchery areas, and stock assessment of neotropical migratory fishes. This research provides valuable insights for fisheries management of continental fish species, emphasizing the efficiency of using maternal transmission as an indicator for estimating contributions from nurseries to fish stock recruitment.

Research efforts focusing on salmonid populations have highlighted the need to better understand demographic parameters for the fry and parr life stages. Monitoring these small fish presents a challenge because negative effects from handling and tagging can bias subsequent parameter estimates. Removal models and associated sampling designs represent one class of mark-recapture models with potential to be applied to very small juvenile salmon, yet existing methods associated with removal studies are not well-suited for all study environments. For example, populations residing in large storage reservoirs may yield low capture probabilities when subjected to removal sampling, making unbiased estimation of survival using traditional removal models difficult. To address this limitation, we developed a sampling design and associated model using parentage-based tagging in hatchery-raised juvenile Chinook salmon (Oncorhynchus tshawytscha) to estimate survival over a 2-year study period in a large storage reservoir in western Oregon, USA. Individual fish were identified to family groups, serving as replicate batch marks in a robust design removal model framework. Results from a simulation suggested that parameter estimates were unbiased even at very low capture probabilities, although the use of model constraints (i.e., covariates or constant parameter values) was necessary to achieve this. Model fitting to field data supported a trend in survival over time, with survival increasing with time since release in the first study year but decreasing in the second.

Anadromous river herring populations, collectively alewife (Alosa pseudoharengus) and blueback herring (Alosa aestivalis), have experienced a multi-century decline in abundance and distribution. These declines have been attributed in part to anthropogenic threats in freshwater ecosystems (e.g., habitat fragmentation, overharvest, water pollution, watershed development). An understanding of variability in juvenile productivity and growth is critical to developing restoration approaches. We characterized variability in juvenile river herring growth among 11 freshwater lakes in the northeastern USA. We used age estimates from otoliths and length measurements to calculate growth rates of juvenile river herring (n = 1452). We tested the effects of juvenile river herring densities, zooplankton (biomass and size), habitat area (based on thermocline depth), and water quality (temperature, nutrients, chlorophyll a) on juvenile growth. Mean monthly growth rates ranged from 0.56 to 1.41 mm/d and typically increased throughout the summer. Increased juvenile growth was best predicted by lower juvenile density (β = − 0.104, P < 0.001) and higher zooplankton biomass (β = 0.032, P < 0.05). Combined with information about juvenile densities and mortality, these results broaden the understanding of anadromous juvenile river herring productivity, provide information that can contribute to refining stock assessment and life cycle models, and help to better understand the potential impacts of habitat conservation and restoration decisions.

Brain form (i.e., brain size and morphology) has been linked to variation in foraging behaviour among species of fishes in lakes and oceans, such as larger brains associated with fish foraging higher in the food chain. However, much less is known about these relationships across habitats, or in stream fishes. Therefore, we explore relationships between foraging behaviour and brain form in the omnivorous creek chub (Semotilus atromaculatus) across different streams of Southwest Ontario, Canada. We assessed foraging behaviour variables (i.e., trophic position, proportion of terrestrial energy in diet and foraging flexibility on aquatic and terrestrial resources) against brain form (i.e., relative brain size and the proportional size of the cerebellum, hypothalamus, olfactory bulbs, optic tectum, and telencephalon). Principal component analysis was used to extract covariation patterns among the size of brain regions. We found that creek chub brain size is positively associated with trophic position and proportion of terrestrial energy in diet, but not foraging flexibility. The first principal component, explaining 91% of size covariation among brain regions, was also positively associated with trophic position but not with proportion of terrestrial energy in diet suggesting that brain regions outside of those measured contribute to the association between brain size and proportion of terrestrial energy in diet. Our results suggest that a relationship between brain size and trophic position may be common among fishes, and that foraging on resources from the terrestrial energetic pathway in streams may present a novel, yet to be characterized cognitive challenge for fish.

Manta rays Mobula cf. birostris aggregate off the Atlantic coast of Florida each spring, typically March through May. Eighteen courtship events were documented and four zooplankton samples collected opportunistically during boat-based and aerial surveys in 2021–2024. Eighty-three percent of courtship events involved only two individuals, and four stages courtship (initiation, endurance, evasion, pre-copulation positioning) were observed. Breaching events were observed on every day, except one, that courtship events were documented by boat survey. All zooplankton samples were dominated by copepods with bivalve larvae, chaetognaths, and echinoderm larvae also being abundant. Zooplankton biomass ranged from 23.9 to 39.6 mg m⁻³. These are the first published records of courtship in Mobula cf. birostris, as well as the first insights into its target surface prey. Identifying potential manta ray critical habitat, such as feeding and reproductive areas, especially in data-deficient regions such as the western Atlantic, is a necessary step for conservation.