Circannual rhythm in the production patterns of three economically important Brachyuran species of crabs

Abstract

ABSTRACT We studied the patterns in production of three species of Brachyuran crabs, namely Scylla serrata, Scylla tranquebarica, and Portunus pelagicus inhabiting the famous Chilika lagoon. We collected data from 3–7 landing centers located in 2–3 different geographical sectors of the lagoon over a period of two consecutive years. Thereafter, we computed monthly averages of production using log-transformed data and performed Cosinor rhythmometry with a fixed time window (τ = 365.25 d) to obtain rhythm parameters, such as Mesor, amplitude, and the peak. The results revealed statistically significant circannual rhythms in the landing biomass of all three species. The circannual rhythm parameters varied across space and time. Of all the landing centers, the Satapada located in the outer channel sector registered the highest production, irrespective of species, although at different times of the year. The spatial and temporal differences observed in the production rhythms between Scylla species and P. pelagicus might be a reflection of optimization of coexistence in their shared niche. This spatiotemporal information on production of the three species of Brachyuran crabs are certainly valuable for building strategies and plans to be implemented during harvesting of those economically very important species that are considered as great Chilika delicacies.