Morfologia, identificação molecular e movimentação do tubarão lombo-preto, Carcharhinus falciformis (Bribon, 1939), no atlântico oeste tropical Recife, 2016

Abstract

The silky shark, Carcharhinus falciformis, is a common species in the pelagic zone, with distribution in tropical and equatorial waters of all the oceans of the world. The objective of this study was to study the ecology of silky shark, including the study of the morphological characteristics, molecular identification and displacement, via electronic taggings of the silky shark in the Southwest and Equatorial Atlantic Ocean, particularly in relation to its distribution in the Saint Peter and Saint Paul Archipelago (SPSPA), in order to clarify their daily and seasonal movement patterns, as well as the local structure of their population. The morphological/anatomical characteristics that define this species was also analyzed in a comparative way with other species of the Carcharhinus genus that also occur in the study area (SPSPA). All tagged shark and collection of biological material were performed in the Southwest and Equatorial Atlantic Ocean, in the vicinity of the SPSPA, in the area between latitudes 00°55'3,72"N and longitudes 029°20'11,22"W. Silky sharks were tagged with three (3) different models of satellite transmitters, totaling ten (10) individuals: 5 MiniPAT (Pop-up archival tags), 3 PSAT (Pop-up Satellite Archival Transmitting Tag), and 2 SPOT (Smart Position or Temperature Transmitting Tag), in the period from 2010 to 2014, in the vicinity of SPSPA. The chondrocrania of Carcharhinus (including Nasolamia), despite being conservative, showed differences that can be taxonomically significant. The cranial components that presented specific consistent differences are: the shape of the rostral node and posterior margin of anterior fontanele, rostral dimension, presence or absence of rostral fenestra, epiphisial notch, epiphisial foramen and nasal flap; direction of the nasal capsules, shapes of the preorbital process and subetmoid fossa. According to Multiplex PCR-technique and to compare its genetic characteristics with the other species of the Carcharhinus genus that are recorded in the (SPSPA) and have close morphometric characteristics (eg C. falciformis, C. galapagensis e C obscurus). The results, based on 64 samples, showed that almost all samples were silky sharks. The tagged sharks showed a preference for warm waters of the mixed layer, where they remained most of the time, during the day. The preferred temperature range of the tagged animal was between 26-28°C, with a preferred depth between 1-10m. Exhibited an elevated residency to the SPSPA, so the present results clearly show the importance of the management measure for the conservation of silky sharks (ICCAT - Interministerial Normative Instruction nº 8 - 06/11/2014), particularly in the vicinity of oceanic islands, due to the strong association these sharks show to these structures.