Environmental Biology of Fishes最新文献

The Atlantic bigeye Priacanthus arenatus is among the main target species by small-scale fisheries in the southwestern Atlantic. Due to its importance to small-scale fisheries, information regarding its trophic ecology is essential for the development of sustainable management plans. Using combined stomach content (SCA) and stable isotope analysis (SIA), the current study examined Atlantic bigeye feeding ecology, including evidence for ontogenetic and intra-annual (i.e. seasonal) diet variation. The diet of Atlantic bigeye was comprised of 16 prey species but was dominated by pelagic crustaceans (53.3% in number) and pelagic fish (19.7%), and benthic crustaceans (11.0%). SCA identified diet variation among seasons (higher dissimilarity in Spring vs. Autumn), which is most likely related to the occurrence of intense coastal upwellings. Significant positive relationships between fish size and δ¹⁵N and δ¹³C values indicated an ontogenetic diet and potential habitat shift; broad isotopic niche area in small individuals (size class I: 115–169 mm) narrowed with increasing body size with the highest niche overlap occurring between size class II (170 to 243 mm) and class III (244 to 308 mm). Overall, the combined SCA and SIA approach determined that the Atlantic bigeye’s diet is closely connected to the pelagic food web. These data provide an improved understanding of ontogenetic and seasonal variation in Atlantic bigeye predator-prey interactions in the southwestern Atlantic.

Mobulid rays are among the most vulnerable of chondrichthyans to overexploitation by fisheries due to their low population growth rates. In locations where catch data are lacking, long-term sightings data can provide valuable insight to infer population trends and status. We recorded underwater sighting data of reef manta rays (Mobula alfredi), oceanic manta rays (M. birostris), and shorthorned pygmy devil rays (M. kuhlii) between 2003 and 2023 in the waters off Praia do Tofo in the Inhambane Province, southern Mozambique, one of the major global hotspots for these rays. We modelled sightings data using a hierarchical generalised linear mixed model framework to account for a suite of environmental variables when examining temporal trends. Raw trend models including only ‘year’ as a predictor showed a 99% decline in sightings of reef manta rays, a 92.5% decline in oceanic manta ray sightings, and an 81.3% decline in devil ray sightings over the 20-year study period. The declining trends persisted for reef and oceanic manta rays once a suite of temporal and environmental variables were accounted for, indicating that the declines were driven by external factors not tested in the models. For shorthorned pygmy devil rays, models that incorporated environmental variables did not retain year as a significant predictor and showed a reduced overall decline in sightings of 36.5%. This indicates that the tested predictors were responsible for approximately half of the observed decline. Anthropogenic factors, particularly fisheries mortality, are likely to have played a significant role in the declining sightings of these three Threatened species. Improved conservation and management measures at a national and international level are critical to prevent further declines, which may otherwise lead to localised extinction.

Estimation of population dynamic rates is one of the most established and widely recognized components of modern fisheries management, yet this information is rarely collected for non-threatened native species. Pejorative views of native, underrepresented fish have contributed to a dearth of research and management efforts for these species. We sought to reduce this knowledge gap for one of the most widely distributed freshwater fish in North America, Freshwater Drum Aplodinotus grunniens (Rafinesque, 1819). We calculated estimates of growth, mortality, and recruitment from lotic environments in the most northern drainage of their range (i.e., Hudson Bay). Our estimates of growth (K, Brody growth coefficient) are similar to studies as far south as Alabama, USA. Estimates of annual mortality (4–10%) and longevity (62 years) are consistent with latitudinal trends observed in the standing literature. We found evidence of recruitment variability (recruitment variability index = 0.53), with a positive association between growing season degree days and year-class strength. Hydrologic variables of discharge during the cold season and rise rate were found to have negative relationships to recruitment. This research gives insight into factors regulating Freshwater Drum populations and will provide useful information for the management and conservation of this widespread but underappreciated species.

Fisheries monitoring, management, funding, and public interest have traditionally focused on game fishes, leading to insufficient data for many non-game freshwater fishes—including lampreys. Conserving lampreys is particularly challenging given their unique life history and propensity for avoiding conventional sampling methods. However, species distribution modeling is an innovative tool that can use historical presence data and spatial data to refine biodiversity monitoring. Here, we created four species distribution models using landscape-scale variables and species occurrence records to predict suitable and unsuitable habitats for extant, native Illinois lampreys. We developed three single-species models and one combined species model that utilized occurrence records from all five extant lamprey species in Illinois. Patterns of suitable and unsuitable habitats for native lampreys indicated similar preferences in habitat. Specifically, maximum temperature values were less than 25 °C and mean soil erodibility was between 0 and 0.5. Urban land cover was in all four models, but the patterns in habitat suitability were not the same across the lamprey species. These models can help natural resource managers prioritize survey sites and determine the contemporary distribution of this imperiled group of fishes.

Despite an increasing interest in a recreational gar (family Lepisosteidae) fishery, little demographic information is available to inform sustainable management practices. Thus, our objectives are to (1) examine the relative abundance of Shortnose Gar Lepisosteus platostomus in the lower Illinois River 1993–2022, (2) estimate the current population structure and vital rates, and (3) estimate the population size through mark-recapture. Estimates of relative abundance were mostly stable or slightly increasing. The total length of Shortnose Gar ranged 30–771 mm and pectoral fin ray ages ranged 1–18 years, with most individuals captured in backwater habitats. Few individuals were recaptured suggesting the possibility of a large population size or a highly mobile population. The mean total length varied among gear types, but gear choice may not have a practical impact on size structure given the high overlap in total length ranges. Pectoral fin ray-derived vital rates suggest that Shortnose Gar in the Illinois River grow slower and have the potential to reach larger body sizes than previously described. Preliminary estimates of mortality rates suggest that fishing mortality remained low for this population as of 2018. The age structure and vital rate findings should be interpreted with caution as pectoral fin rays likely underestimate the age of Shortnose Gar but provide valuable baseline data for future comparisons. Future research should utilize otolith age estimates, determine exploitation levels, and assess movement ecology to better inform management strategies that provide for sustainable harvest of Shortnose Gar.

Researchers, managers, and policymakers have historically neglected non-game fishes relative to game fishes, and this oversight has extended to invasive non-game fishes in the United States. One such fish—the Eastern Banded Killifish (Fundulus diaphanus diaphanus Lesueur 1817)—has established and rapidly spread in Lake Michigan and connected waters since 2000. Here, we assess potential drivers of the successful invasion of Eastern Banded Killifish, as well as their potential to disrupt native communities and food webs. Specifically, we compare the trophic niche breadth and diet composition between Eastern Banded Killifish and a native subspecies, Western Banded Killifish (Fundulus diaphanus menona Jordan and Copeland 1877), using stable isotope and gut content metabarcoding analyses. Stable isotope analysis showed that Eastern Banded Killifish had a higher variance in littoral dependence and trophic position than Western Banded Killifish, but both stable isotope and gut content metabarcoding analyses revealed an overlap in the diet composition and trophic position between the subspecies. Eastern Banded Killifish may successfully establish outside its native range due to higher feeding variability than Western Banded Killifish, including in habitats historically unused by the native subspecies, but the trophic niche between these two subspecies was similar overall. This study provides insights into the successful invasion of a potentially overlooked non-game fish—Eastern Banded Killifish—while also comparing stable isotope and gut content metabarcoding analyses for an invasive freshwater fish for the first time.

The elasmobranch fishes, both the sharks and rays, which inhabit the underwater environment, display breaching behaviors consisting of their sudden propulsion out of the water and into the air. They then land on top of the sea surface, displacing water upon contact. At other times, they do not completely clear the water, but partly so, performing a lunge rather than a clear jump or breach. These behaviors have been reported in the scientific literature for the fast-swimming predatory sharks, but also for a slow-swimming planktivorous shark as well as many of the rays. We identify breaching behavior in species in the selachan families, Alopiidae, Carcharhinidae, Cetorhinidae and Lamnidae, and batoidan families, Mobulidae, Aetobatidae, Myliobatidae, Rhinopteridae, and Dasyatidae. We present and discuss evidence in support of the following functions: (1) parasite removal, (2) clearing of gill rakers, (3) expulsion of feces or internal parasites, (4) courtship, (5) attraction of conspecifics, (6) repelled by conspecifics and interpecifics, (7) evasion by conspecifics, (8) feeding, (9) concentrating or stunning of prey, and (10) birthing. Our recording of this behavior has evolved beyond simple observations and now incorporates information gathered through advanced technologies, such as animal-borne data loggers, digital photography, and observations from aerial or underwater drones. Within this context, we review the relevant literature, describing studies and research to provide additional insight into the causation of these behaviors.

The combination of the physical structural heterogeneity of the environment, oceanographic characteristics, and the benthic assemblage composition structures the habitat, consequently shaping the associated diversity of fish. Understanding the spatial variability of fish assemblages and how it relates to environmental factors is essential to identify potential variables that determine spatial patterns and predict impacts on fish assemblage metrics, thus providing valuable information for management. Here, we investigated reef fish micro-scale spatial distribution around Alcatrazes Island in the subtropical region of the Southwest Atlantic, Brazil. Multivariate Regression Trees were fitted to explore the effects of structural heterogeneity, wave power, depth, water temperature, and benthic cover on the structure of reef fish assemblages, addressing composition, richness, density, biomass, trophic groups, mobility, and conservation status. Our results suggest that depth, turf, and coral cover were the main predictors of fish assemblages in rocky reefs at Alcatrazes Island, revealing five distinct fish assemblages with different habitat preferences. These results provide additional insights into the relationship between reef fishes and their environment, providing empirical evidence for decision-makers to implement spatially based management policies, especially to prioritize zones for conservation along the island.

The impact of global warming on the initial growth and development of fish, including sturgeons, is evident. The embryonic development phase is crucial for the preservation and propagation of the Chinese sturgeon, yet the specific influence of water temperature on this process remains inadequately documented. This study conducted experiments using three temperature groups (16, 19, and 22 ℃) to investigate the impact of temperature on the embryonic development of Chinese sturgeon. Subsequently, five statistical models were utilized to fit the developmental data through regression analysis, in order to determine the correlation between incubation time and temperature of the embryos. Data from cultured Chinese sturgeon embryos were finally utilized to validate water temperature development indices. Over the temperature range of 16–22 ℃, water temperature was positively related to the rate of embryonic development in Chinese sturgeon. The time to hatching in the group experiencing the highest temperature (22 ℃) was nearly cut in half in comparison to the group exposed to the lowest temperature (16 ℃). Among the five regression models, the S (sigmoidal) model was the best for predicting the incubation period of Chinese sturgeon embryos from temperature (R² = 0.939, p < 0.01). Based on the progression from incubation to initial hatching, we estimated daily development indices, ranging from 10.66 to 32.22% between 14 and 25.9 ℃. The water temperature development indices of Chinese sturgeon established in this study have the potential to improve the accuracy of predicting hatch timing and the transfer of fish fry, thereby aiding in the conservation and enhancement of Chinese sturgeon resources.

The weaving of diverse knowledge systems, including Indigenous, Local, and Western Knowledge, is an increasingly adopted approach in scientific research and is perceived as a promising path towards advancing knowledge and management of coastal areas and fisheries management in Canada. Despite documented successes, skepticism among scientists and decision-makers persists, leaving unaddressed gaps. Here, in response to concerns voiced by fishers from the Mi’gmaw community of Ugpi’ganjiq, the Gespe’gewa’gi Institute of Natural Understanding (GINU) co-created a project to improve understanding of the ecology and state of the threatened Gumegwsis (i.e. Cyclopterus lumpus, common lumpfish) in inner Mawipoqtapei (Chaleur Bay, Eastern Canada). Through a Two-Eyed Seeing approach, we combined semi-structured interviews with five Knowledge Holders with a literature review, mapping, and temperature monitoring. Utilizing this Mi’gmaw framework, we learned about Gumegwsis life history in inner Mawipoqtapei, its significance to local fishers, changes in abundance over time, threats to the species, and identified potential areas for spawning and nursery habitats. Prior to our project, the Committee on the Status of Endangered Wildlife in Canada (COSEWIC) assessment asserted “There are no indications of any ceremonial uses of Lumpfish in Canada and there is no ATK (Aboriginal Traditional Knowledge) information available”. In contrast, our study reveals the distinctive relationship and comprehension of Gumegwsis held by Mi’gmaw fishers, underscoring the significance of embracing multiple ways of knowing towards understanding species ecology, and presenting a compelling case for co-creation of species recovery strategies and collaboration in fisheries research.