Meeting Abstract
92.5 Thursday, Jan. 7 Coupling GPS tracking with dive behavior to examine the relationship between foraging strategy and fine-scale movements KUHN, C. E.*; TREMBLAY, Y.; REAM, R. R.; GELATT, T. S.; National Marine Mammal Laboratory, NOAA; Centre de Recherche Halieutique Méditerranéenne et Tropicale; National Marine Mammal Laboratory, NOAA; National Marine Mammal Laboratory, NOAA Carey.Kuhn@noaa.gov
The foraging behavior of diving marine species is often categorized into three fundamental groups: epipelagic (mid-water feeding), mesopelagic (deep-water feeding), and benthic (feeding on the bottom). Since these foraging strategies are shaped in part by the distribution and behavior of prey, we tested the hypothesis that searching behavior and space use will differ depending on the foraging strategy employed. Northern fur seals (Callorhinus ursinus) were used as a model, as individual fur seals can display both epipelagic and benthic foraging strategies in distinct bouts over the course of a single foraging trip. Dive bouts were characterized into foraging strategies based on numerous dive parameters (e.g. depth and bottom time). For each strategy we compared movement patterns (e.g. transit rate and path straightness) and space use (the size and intensity of area-restricted search zones [ARSZ]). Foraging strategies were significantly different for all dive and movement parameters measured but did not differ in overall space use. For example, benthic bouts were composed of deeper dives (78.1±1.6 vs. 22.2±0.5m) with more time in the bottom phase (62.7±1.6 vs. 48.4±0.9sec). During epipelagic bouts females traveled at a slower rate (4.6±0.1 vs. 5.1± 0.2ms-1) and followed a more sinuous path (straightness index: 0.88±0.01 vs. 0.95±0.01). On average only 1.4±0.1 ARSZ were identified per trip and the characteristics of epipelagic and benthic ARSZ were not significantly different. This study suggests the pooling of these fundamentally different foraging behaviors may result in the masking of small changes that may be critical for species management.
