A pilot study of deepwater fish movement with respect to marine reserves

Abstract

Background: The spatial ecology of deepwater demersal teleosts is poorly understood, and this group of fishes has rarely been studied using conventional or electronic means to discern movement and migration. Likewise, the development of management tools for such species has received less attention as compared to shallow water species, and there are few fishery closed area systems developed for the purpose of managing deepwater demersal fishes. The eteline snappers, which occur in depths of 100 to 400m, are an important fishery resource throughout the tropical Pacific, and are believed to be vulnerable to over-exploitation. Results: Deepwater eteline snappers were tagged with acoustic transmitters and detected on a network of listening stations that encompassed a fishery closed area in the Main Hawaiian Islands. Differences were detected in movement between species, with the bentho-pelagic Etelis coruscans moving more frequently and over slightly longer distances (1.4 movements/day detected, interquartile range (IQR) 0.0-2.4; maximum distance 4.7km, interquartile (IQR) 4.7-6.4km) than the demersal Etelis carbunculus (0.0 movements/day detected, interquartile range 0.0-0.3; maximum distance 4.7km, interquartile range 4.6-4.7km). The maximum single movement distance was 8.9km for E. coruscans and 4.7km for E. carbunculus. The median length dimension for bottomfish closed areas in the Main Hawaiian Islands is 9.2km (IQR) range 7.3-13.0km). Conclusions: Knowledge of the spatial ecology of animals is essential to understanding the effects of spatial management measures such as marine reserves. Differences between species indicate that effective reserve size will differ depending on the species. These results suggest that the reserves set up for bottomfish in the Main Hawaiian Islands are likely to have effects in reducing fishing mortality for E. carbunculus due to its low rate of cross border movement.