Seasonal Shifts: Tracking Fish Larval Diversity in a Coastal Marine Protected Area

Abstract

This research explored the influence of seasonal and environmental variables on the variation and density of ichthyoplankton in the Thermaikos Gulf and the adjacent marine protected area of the Litochoro artificial reef in Pieria, northern Greece. The objective was to assess the condition of existing ichthyoplankton communities, understand their relationship with seasonal environmental parameters, and ascertain whether the area plays the role of a fish nursery site. Observations were carried out on the boundary of the marine protected area near Litochoro, with collection sessions occurring during the spring, summer, and fall seasons from 2018 to 2021. Ichthyoplankton was collected using a bongo net sampler across 16 stations, identifying seventy larval fish species. Measurements of physico-chemical parameters were taken as well as community and population metrics such as species abundances. In the Litochoro area, the interplay between environmental conditions and the dynamics of ichthyoplankton species highlights significant ecological trends. Notably, commercially important species such as Engraulis encrasicholus (anchovy) and Sardina pilchardus (sardine) exhibited peaks in abundances, with anchovies reaching up to 544/10 m2 in May 2021 and sardines peaking at 383/10 m2 in April 2020. These species are crucial both ecologically, as integral components of the marine food web, and economically, serving as primary targets in local fisheries. Spearman analysis showed some species like anchovy having a negative trend with chl-a values. Also, diversity indices had strong negative correlations with chl-a values, suggesting that higher chl-a concentrations might be associated with lower biodiversity whereas most diversity indices, apart from Pielou’s normality index (J) and Simpson’s diversity index (1–lambda), showed a significant positive correlation with surface salinity. This suggests that increased salinity levels might boost certain facets of biodiversity during the summer and early autumn months.