Biological characteristics and relative abundance of shrimp Plesionika edwardsii on the northeast coast of Brazil

Abstract

The analyzed data represent the first piece of information regarding the abundance of Plesionika edwardsii in the western part of the South Atlantic. Six hundred forty-one individuals were analyzed, 59.6% of them male and 40.4% female animals. Distribution of abundance of the shell lengths of both genders was single modal. The male animals presented increased occurrence in the class of 16-17 mm, with amplitude between 9 mm and 25 mm (average 17.8 mm), whereas female animals were more frequent in the class of 22 to 23 mm, with variation between 12 mm and 29 mm (average 20.7 mm). The number of male animals was higher in the range of the classes between 8 and 19 mm; no male animals were registered with their length exceeding 25 mm. From 19 mm, the number of female animals was higher than the number of male animals, in all the different classes. The ratio between weight x length showed the determination coefficient r² = 0.89, with tendency towards an exponential curve. The ratio between the shell length and the overall length showed the coefficient of r² = 0.93, with tendency towards a logarithmic curve. The female animals were not only larger, but they were also heavier than the male animals, both in the lower sea depths (100-300 m) and in the deeper regions (300-500 m) (P = 0.001 and P = 0.001, respectively). The CPUE (Catch per Unit Effort) between 100 and 200 m was significantly higher (P = 0.03). Distribution of the P. edwardsii population was observed in function of the topography of the continental slope of the Brazilian Northeast, which reveals the necessity of further studies on the biology of these and other deep-sea species in order to be able to better understand their role in the ecosystem of the ocean.