Moon and tidal influences on catch composition of fishes in one tidal flat of the Paranaguá Bay, Paraná, Brazil

Abstract

In a tidal flat of the Paranaguá Bay, the influence of the tide and lunar phase on the capture of fish was analyzed. The collections were accomplished in the high tide and low tide of the syzygial (full moon) and quadrature (waning moon) tides, between August 1998 and July 1999. At all collection moments, two tows were made parallel to the coast, in the direction of the current, in 100 m long areas marked on the beach beforehand, using a seine net of 30.0 m x 2.0 m with a mesh of 0.5 cm between adjacent knots and a 2 m long bag. A total of 47,012 fish specimens were captured (179 kg), belonging to 110 species from 43 families. The mean number of species captured was significantly higher at full moon, while the mean diversity and equitability were statistically higher at high tide. On average, the size and weight of the fishes were also larger in the full moon and in the high tide. Between the phases of the moon and the two tides, statistical differences were not observed among the averages of the number of fish, weight of the capture and richness. The species structures were different between the captures at the low tide and high tide of the full moon and between the low tide of the full moon and the high tide of the waning moon. During the latter, the largest mean dissimilarity was observed, and the species that more contributed to this dissimilarity were Anchoa tricolor and Anisotremus surinamensis.