The mortality of the bottlenose dolphin, Tursiops truncatus, on the southern portion of Rio Grande do Sul State coast was investigated based on 914 beach surveys conducted between 1969 and 2006. A total of 188 stranded bottlenose dolphins were recorded during this period, indicating a 1.8M:1F sex-ratio of those animals sexed (N = 79). Mortality was low in calves, high in juveniles and sub-adults and slightly lower than in adults. The overall mortality was clearly seasonal overlapping with higher fishing efforts in the Patos Lagoon Estuary and adjacent coastal areas, where most individuals washed ashore. Analysis of a continuous 14-year long subset (1993–2006) of the data indicated relatively low levels of mortality between 1995 and 2000 and a marked increase between 2002 and 2005 followed by an apparent drop in 2006. By-catch was responsible for at least 43% of the recorded mortality between 2002 and 2006. Juvenile males were more susceptible to incidental catches. Among females, by-catch of adults represented 75%. Results of a potential biological removal analysis suggest that current levels of fishing-related mortality are unsustainable for the small resident population of bottlenose dolphins that inhabits the Patos Lagoon Estuary, and that this population may be declining.

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The leatherback sea turtle (Dermochelys coriacea) population that nests in Brazil is restricted to a few individuals, but high densities of pelagic individuals are observed along the southern and southeastern Brazilian coast. We investigated the diversity of the mitochondrial DNA (mtDNA) control region in order to understand the relationship between nesting and pelagic leatherbacks from Brazil and elsewhere. High-quality 711-bp sequences were generated, analyzed, and compared with published data from worldwide populations. We detected the presence of shared haplotypes between nesting and pelagic aggregates from Brazil, as well as haplotypes shared with other nesting areas from the Atlantic and Pacific. Furthermore, the use of longer control region sequences allowed the subdivision of the common Atlantic haplotype A into 3 different haplotypes (A1, A3, and A4), thus improving the resolution of mtDNA-based leatherback phylogeography. The use of longer sequences partially supported a closer association between nesting and pelagic individuals from Brazil and pointed to a complex origin for the pelagic individuals in the Brazilian coast.

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1 The term "stranding" is generally used when the animal(s) is (are) still alive when reaching the beach, however, here the term will also refer to dead animals that were washed ashore.