Sex and Length as Predictors of Vertical Movements in Smalltooth Sawfish (Pristis pectinata)
Smalltooth sawfish (Pristis pectinata) are a marine species of high concern since they are listed as critically endangered species by the International Union for Conservation of Nature (IUCN) and listed as endangered under the U.S. Endangered Species Act (ESA). Smalltooth sawfish are extremely vulnerable to being caught as bycatch due to their long, toothed rostrum that can easily become entangled in fishing nets, especially in shrimp trawling fisheries. Several studies have been conducted on smalltooth sawfish since being listed under the ESA in 2003, but their vertical movements and use of depth have still not been thoroughly studied. Until recently, sawfish were thought to stay at a depth of 10 m or less, but studies have now shown that they occupy much deeper depths. Due to these conflicting findings in the literature, depth was chosen to be the focus of this study. Furthermore, this study investigates whether sex or individual total length has an influence on the percentage of time a sawfish spends at a particular depth. Satellite telemetry was used to track the movements of the tagged sawfish (n=14). The data collected from the pop-off archiving satellite tags (PSATs) showed smalltooth sawfish spend most of their time in shallow water (between 0-8 m), but do frequently occupy deeper depths. Sex was found to be a significant factor, while total length was not. Females were found to spend more time at deeper depths than males. Understanding how sawfish use depth is important in order to predict population trends and dynamics. Knowing the factors that affect a sawfish’s depth use would be beneficial to efforts that manage and conserve this species. With the decline of smalltooth sawfish and their vulnerability to population loss, more research needs to be conducted to create more effective management and recovery plans.