Search Results (4)

Estuaries are vital coastal ecosystems that support fish during key life stages such as spawning, feeding, and early development. This study investigates ichthyoplankton composition and abundance in the Sanquianga Tapaje estuarine system, located in the southern Eastern Tropical Pacific (ETP) of Colombia. Zooplankton samples were collected using bongo nets at 11 stations across four river mouths (Tapaje, Amárales, Sanquianga, and Guascama), alongside measurements of oceanographic parameters at 1 and 10 m depths. A total of 357 fish larvae were identified, representing 23 species and 11 families, with Engraulidae, Gobiidae, and Carangidae dominating the assemblage. Water column conditions reflected typical tropical estuarine dynamics, influenced by tidal action and freshwater input. Spearman’s rank correlation revealed strong positive associations between larval abundance and surface salinity (r_s = 0.81, p = 0.003), as well as dissolved oxygen saturation and concentration (r_s > 0.68, p < 0.021). Diversity indices (Shannon, Pielou, Whittaker) indicated high species turnover in transitional zones, and larval hotspots were associated with outer estuarine zones. Salinity and dissolved oxygen emerged as key drivers of ichthyoplankton distribution. These findings underscore the ecological complexity and nursery function of tropical estuaries, offering baseline data to inform biodiversity conservation, ecosystem monitoring, and adaptive management in Colombia’s Pacific region and across the ETP. Full article

The seasonal and interannual temporal variation in the composition, richness, diversity, and similarity of fish larval assemblages associated with an Eastern Tropical Pacific (ETP) coral reef system was studied in March (cold water) and September (warm water) during the years 2017, 2018, and 2019. Throughout the study period, we collected 4779 fish larvae and identified 88 taxa, encompassing 46 families. This increased the total number of recorded fish taxa for the region to 146. Fish larvae were collected by daytime and nighttime surface trawls, using a bongo net 30 cm in diameter and 180 cm in length, equipped with mesh sizes of 300 and 500 μm. The species diversity and abundance of ichthyoplankton over this ETP coral reef changed by intra-annual variation of the hydrological conditions of the upper layer of the sea. Six significant assemblages were identified (SIMPROF, p < 0.05), each one associated with each sampling period (ANOSIM, R = 0.764); Cetengraulis mysticetus, Diaphus pacificus, Anchoa sp., Anisotremus sp., Bremaceros bathymaster, Oligoplites saurus, Caranx sp., Seriola sp., Gobiidae sp., Microgobius sp., and Synodus evermanni were the species that contributed to dissimilitude between groups. Canonical correspondence analysis revealed significant associations between specific larval fish taxa abundance and temperature, salinity, dissolved oxygen, and zooplankton biomass. Overall, the assemblage of ichthyoplankton in this ETP coral reef system is sensitive to seasonal changes in water column hydrographic conditions. Full article

Differences in fish assemblages’ composition and their relationship with the environmental variables were analyzed in the Urías estuarine system, Mexican North Pacific. Environmental variables and fish catches were recorded bimonthly between June 2018 and November 2021, including a period before and during the COVID-19 pandemic. Multivariate analyses were performed in the studied area to define zones based on their environmental, biotic, and abiotic characteristics and the effect of these on the fish assemblages. Two zones were identified, an estuarine with mangrove forest and a surf zone in the coastal area outside the estuarine system. Fish composition, biomass, and diversity (α and β) were evaluated among the factors of the period (before–during COVID-19), climatic seasons, and zones. A total of 5947 fish individuals of 41 species were collected using beach seines as fishing gear. The structure of the fish assemblages was different between zones and periods. Abiotic (temperature, salinity, and total matter suspended), biotic (mangrove area), and temporal (season and period before–during COVID-19) variables had an effect on fish biomass and α diversity, while the results of the β diversity only indicate changes in the nestedness component before–during the lockdown. These results indicate a change in fish assemblages’ structure and composition between periods, which might be a consequence of the limitation of human activities derived from the pandemic, climatic changes, or a combination of both effects. Our results show that fish assemblages in the estuarine systems of the Tropical Eastern Pacific are unique, and there is a need to establish local management strategies for these ecosystems. Full article

Oceanic islands harbor unique yet fragile marine ecosystems that require evidence-based environmental management. Among these islands, the Galapagos archipelago is well known for its fish diversity, but the factors that structure communities within and between its islands remain poorly understood. In this study, water quality, physical habitats and geographical distance were assessed as potential predictors for the diversity and structure of fish assemblages. Differences in the structure of fish assemblages of the two studied islands (Santa Cruz and Floreana) were most likely driven by temperature and nutrient concentrations. In the relatively highly populated island Santa Cruz, the structure of fish assemblages was more affected by water conditions than physical habitats while the contrary was true for the more pristine area of Floreana. A wide variety of species with different geographical origins were distributed over the different islands, which indicates that most fish species are able to reach the islands of the archipelago. However, temperature gradients and elevated nutrient levels cause large differences in the structure of local fish assemblages. In addition, in Santa Cruz nutrient concentrations were negatively correlated with $\alpha$ diversity. Since pollution is a clear pressure on the fish assemblages of oceanic islands, environmental management of the coastal areas is of paramount importance. Full article