Abstract
The primary objective of this study was to investigate the seasonal fish and crustacean variations concerning taxonomic composition, species richness, and diversity in sandy beach habitat. For this purpose, we investigated the Sonmiani Hor lagoon area during four distinct seasons, i.e., northeast (NE) monsoon, pre-monsoon, south-west (SW) monsoon, and post-monsoon for one year. During each haul, the net was pulled about 100m along the beach in 0.5m depth. The results showed a strong linear correlation between the diversity index and equitability in fishes (r = 0.978). The diversity index was strong negatively correlated with the abundance and biomass (r = -0.978, -0.972, respectively). The physical attributes like sea surface water temperature and salinity showed a strong negative effect on species assemblages (r = -0.981 and -0.943, respectively). The mean air and water temperature illustrated approximately 3°C difference during NE and pre-monsoon seasons. However, salinity, pH, and electrical conductivity did not show any significant seasonal variabilities. Under the ecological indices, the fish species displayed higher diversity (H' = 3.19) during SW monsoon, whereas the lowest diversity was observed during pre-monsoon (H' = 1.58). The equitability and species richness, however, remained more noticeable during SW monsoon (J' = 0.81). The total number of individuals of fish and crustaceans reached 4799 with 3813 fish individuals and 986 individuals of crustaceans. A total of 27 families of fish while five crustacean families comprising of 30 genera and 38 fish species while ten genera and 17 species of crustaceans were recorded. Liza subviridis displayed the highest abundance among the sampled fish species. In conclusion, fish species constituted a significant part of the coastal fauna in the study area. The seasonal variations displayed distinct variations in fish species composition and diversity.
Highlights
The patterns of the spatial distribution of fish and crustaceans along the sandy beaches often allude to the degree of disturbance as shallow bays and beaches are the coastal ecosystems most threatened by the anthropogenic activities and habitat changes (Omena et al, 2012; Equbal et al, 2018)
The water temperature (WT) has a strong association with air temperature (AT); the mean lowest temperature was recorded during NE monsoon (15.68°C)
Fish species displayed higher diversity (H’ = 3.19) during SW monsoon, whereas the lowest diversity was observed during pre-monsoon (H’ = 1.58)
Summary
The patterns of the spatial distribution of fish and crustaceans along the sandy beaches often allude to the degree of disturbance as shallow bays and beaches are the coastal ecosystems most threatened by the anthropogenic activities and habitat changes (Omena et al, 2012; Equbal et al, 2018). The fish species display relatively fewer variations with seasonal and temporal fluctuations (Kim et al, 2019; Saeed et al, 2020; Atique et al, 2020a; Khanom et al, 2020), shallow intertidal zone fish communities. The crustaceans, such as crabs, are considered for research to reflect upon seasonal and temporal changes (Post et al, 2006; El Asri et al, 2018; Rahman et al, 2020). Gibson et al (1993) alluded to the community variations in the sandy beaches in Scotland linked with environmental changes that unfold the annual and seasonal distribution patterns in fish and macro crustacean populations Most of the studies report benthic invertebrates, whereas sampled fish species are mostly those of commercial importance (Kouadio et al, 2008; Cuéllar-Mercado et al, 2019). Gibson et al (1993) alluded to the community variations in the sandy beaches in Scotland linked with environmental changes that unfold the annual and seasonal distribution patterns in fish and macro crustacean populations
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