Factors affecting striped marlin catch rate in the New Zealand recreational fishery

Abstract

A 25-year time series of striped marlin catch per unit effort (CPUE) data has been collected from gamefish charter skippers fishing the north-east coast of New Zealand. The CPUE averaged over the whole gamefishing season ranged from 0.053 striped marlin per charter boat day in 1984–1985 to 0.269 striped marlin per charter boat day in 1998–1999. This study investigates the amount of the variability in gamefish charter CPUE that can be explained by environmental and fishing-related factors for the period 1981–1997. Factors investigated were sea surface temperature during the fishing season, El Niño southern oscillation index, the position of the 20°C isotherm at the beginning of the fishing season, annual commercial catch of striped marlin in the New Zealand 200 mile zone and surface longline CPUE in the wider south-west Pacific. A stepwise multiple regression was used to develop a model of recreational striped marlin CPUE to determine the factors that best accounted for the variation observed. Surface longline CPUE in the general south-west Pacific (10°S–40°S latitude, 165°E–160°W longitude) had the strongest correlation with recreational CPUE (P = 0.001), but a poor correlation was found with longline CPUE from the western Tasman Sea and Coral Sea (10°S–40°S latitude, 145°E–165°E longitude). The total surface longline catch of striped marlin in New Zealand each season was negatively correlated with recreational CPUE (P = 0.019), which indicates a possible interaction between these fisheries.