Preparation of the Northeast Fisheries Observer Program Gillnet Data for Use in Bycatch Analyses of Protected Species

摘要

Bycatch analyses of protected species (marine mammals, sea turtles, and seabirds) in domestic commercial fisheries off the Atlantic coast of the USA are usually conducted using data collected by the Northeast Fisheries Observer Program (NEFOP). In this paper, the preparation of a standard dataset of the 19892006 NEFOP gillnet data is described for use in bycatch estimation. Dressed landed weights were converted to live weights using established conversion factors, resulting in a 3.76% increase in observed weights in the NEFOP gillnet database. Data on additional variables such as bathymetry, sea surface temperature, chlorophyll a concentrations, oceanographic fronts, and distances from the coastline and bottom depth contours were obtained through Geographic Information Systems. Approximately 93% of missing depth and sea surface temperature values were replaced by GIS-acquired values. Other missing values were imputed through medians from representative strata. The standard dataset will reduce data preparation effort for bycatch assessments and enable consistency and reproducibility of bycatch estimates and other related analyses.