Benthic Habitats and the Effects of Fishing

Abstract

We conducted a 9-day field test of laser line-scan imaging technology (LLS) to investigate benthic marine habitats in and around the Big Creek Ecological Reserve (BCER) off the central California coast. We determined the utility of LLS for determining the distribution and abundance of fish and megafaunal invertebrates, and identifying habitats and species associations by comparing LLS images with those acquired from side-scan sonar and a remotely-operated vehicle. We also evaluated the ability of LLS to detect seafloor disturbance caused by fishing trawl gear. We surveyed a 2.6 km long x 0.4 km wide area inside and directly outside BCER. With the laser we imaged isolated rock outcrops with patches of large Metridium sp., dense schools of fishes, drift kelp, sea pens, salp chains, and sedentary benthic fishes (possibly California halibut, Pacific electric ray, ratfish and juvenile lingcod.). The LLS system offers the advantage of imaging both the biogenic and abiotic components of habitat, and depicts their spatial relationships with detail that currently is not possible using acoustic imaging techniques such as side-scan and multibeam sonar. LLS imagery also provided fine detail of low relief shelf geology such as sand waves and ripples; evaluating these features in a broader context from a post-processed mosaic of the study area could help us understand coastal physical processes that influence dynamic benthic habitats.