Fishery-SCUBA Comparisons

Collaborator: Mark Carr –  Raimondi/Carr Lab (UC Santa Cruz)

Area-based fishery management and ecosystem-based management strategies are beneficial marine resource management tools, but require finite information about the structure and function of ecosystems to evaluate populations and describe ecosystem effects of fishing. The required information is unlikely to be obtained from sporadic, fishery-dependent data collected from data-poor fisheries, and it is expensive to conduct extensive fishery-independent surveys. This situation has led to an interest in relating or combining information from a variety of disparate sampling methods.

From 2003-2006, we investigated relationships between estimates of catch-per-unit-effort (CPUE) and abundance generated from typical nearshore commercial fishing operations and estimates of density and abundance derived from SCUBA surveys in the same locations. Relationships among CPUE estimates from different sampling methods were found to be statistically significant in the case of many of the common species sampled across sites in Carmel Bay, CA. The compounding effects of within-sample variance and the error associated with regression equations, however, would result in poor confidence in values translated from one sampling method to another.

Our results indicate that different sampling methods may each provide reasonable estimates of population trends, but are sufficiently different and variable so as to preclude the use of a scaling factor to standardize population estimates among sampling methods. Also, differences in species composition (i.e., relative CPUE among species) recorded by each gear type were significant among sampling methods and were also affected by habitat relief and sample depth. Nonetheless, our results suggest the promise and value of a cost-benefit analysis that could allow managers to design optimal sampling strategies for characterizing CPUE relationships within a region of interest. A sampling program that benefits from the complementary strengths of both fishing gear and SCUBA sampling will likely result in the most comprehensive description of nearshore fish assemblages.

Starr, R.M., M. Carr, D. Malone, A. Greenley, and S. McMillan.  2010.  Complementary Sampling Methods to Inform Ecosystem-Based Management of Nearshore Fisheries. Marine and Coastal Fisheries: Dynamics, Management, and Ecosystem Science. 2:159–179.