Smalltooth sawfish (Pristis pectinata Latham, 1794) in the Casamance River, Senegal: A historical perspective

Abstract

Abstract A study of euryhaline elasmobranchs was conducted in the Casamance River, southern Senegal, between June 1974 and October 1975. Data were collected from 159 sawfish, comprising 158 smalltooth sawfish (Pristis pectinata Latham, 1794) and one largetooth sawfish (Pristis pristis Linnaeus, 1758). The mean total rostral tooth count for P. pectinata was 46 (range 41–53), significantly lower than the total tooth counts for the western Atlantic population. No sexual dimorphism in rostral tooth counts was apparent, in contrast to findings from the western Atlantic. The total rostral length averaged 22.9% of the total length. One hundred and forty‐four individuals were caught within the river system itself, all of them were juveniles. Fifteen adults, including the single largetooth sawfish documented during the study, were caught at the river mouth or at sea. Six sawfish, caught between May and July, bore rostral sheaths, indicating that they had recently been born. Although the Casamance and Gambia rivers are only 120 km apart, the findings from this study combined with published data collected from the Gambia River during the same period suggest the partitioning of juvenile habitats by the two sawfish species present in the region, to the level of different river systems. Both species are likely to have used the same coastal habitats as adults. The Casamance River was clearly an important habitat for smalltooth sawfish some 40 years ago, but it is unknown whether the species persists there. Intensive artisanal fisheries for sharks and rays in the region poses a significant threat to any remaining sawfishes, and a challenge for elasmobranch fisheries management.