Ontogenetic variation in the sagitta otolith of Centropomus undecimalis (Actinopterygii: Perciformes: Centropomidae) in a tropical estuary

Background. The presently reported study was initiated in order to increase the available information on this species of commercial and sporting importance, thus the study aimed to identify possible differences in the shape of the sagitta otolith during the ontogenetic development of the common snook, Centropomus undecimalis (Bloch, 1792), sampled between May 2017 and April 2018 at the mouth of the São Francisco River along its estuary stretch (approximately 10 km). Morphometric study of otoliths is important as a support for future studies on the trophic ecology of ichthyophagous fishes and studies on fishing stocks using the contour of otoliths of this species. Materials and methods. The fish were sampled monthly at five sampling sites distributed between the mouth of the São Francisco River and the municipality of Brejo Grande. For the collection, a beach seine (30 m long, 2.8 m high, and 5 mm mesh between opposite knots) was used. In the laboratory, the otoliths were extracted, photographed, described morphologically, and the possible differences in their contour were analyzed using the wavelets. Results. We analyzed 148 otoliths grouped into six class intervals. Otolith shape varied from rounded to trapezoidal during the ontogenetic growth and showed a gradual decrease in the percentage of presence of the excisura ostii (absent in the largest specimens). PERMANOVA evidenced significant differences in the contour between the smallest size class and the others. For wavelet 4, the LDA correctly reclassified 47.97% otoliths in the size classes, with the best reclassifications occurring in the 5.0–10.0 (43.33%) and 10.1–15.0 cm (65.52%) intervals. While for wavelet 5, the LDA correctly reclassified 59.46% otoliths according to the size class, with the best reclassifications occurring in the length classes 5.0–10.0 (46.67%), 10.1–15.0 (75.86%), 15.1–20.0 (66.67%), and 20.1–25.0 cm (59.38%). Conclusion. The ontogenetic differences found both in the shape and in the otolith structures are important for the enhancement of knowledge on fish biology and indicate the need for further studies. The lack of such information on estuarine species makes it difficult to conduct studies on the trophic ecology and the management of these species

Assessment of larval distribution of invasive omobranchus punctatus (Valenciennes, 1836) (Pisces: Blenniidae) in a subtropical estuary (Southern Brazil)

The occurrence and spatio-temporal distribution of the larvae of exotic Blenniidae Omobranchus punctatus (Valenciennes, 1836) was studied at Babitonga Bay, a subtropical estuary of Southern Brazilian Coast. Samples were collected in 26 ichthyoplankton surveys (28 stations) from April 2004 to August 2008. Oblique hauls were used, with both a conical plankton net fitted with 200µm mesh and by a cylindricalconical plankton net fitted with 500µm mesh (two and five minutes hauls, respectively). Larvae occurred continuously throughout the sampling and an increase in density was observed in the period from November to April. Specimens were registered throughout the study area. The occurrence of a wide range of ontogenetic stages indicates that the species is maintaining the population within Babitonga Bay. The lack of information about the potential impacts of O. punctatus in the ichthyoplankton assembly, with regard to ecological interactions and the food chain suggests the need for further studies