Catch Temperatures for Some Important 

 Marine Species off California 



JAMES L. SQUIRE, JR. 



ABSTRACT 



Airborne sea surface temperature surveys using infrared techniques were conducted monthly off the central and 

 southern California coast, 1963 through 1968, by the National Marine Fisheries Service in cooperation with the U.S. 

 Coast Guard. The resulting temperature data were matched to commercial sportfishing boat catch data to determine 

 the relationship between catch and temperature for the following major sport species: chinook and silver salmon, 

 Oncorhynchus tshawytscha and O. kisutch; yellowtail, Seriola dorsalis; Pacific bonito, Sarda chiliensis; Pacific bar- 

 racuda, Sphyraena argenteai white seabass, Atractoscion nobilis; and albacore, Thunnus alalunga. 



Part I presents graphs for each of the above species for areas having high catches, the month during which most 

 fish were caught, sea surface temperature at which most fish were caught, mean catch temperature and its standard 

 deviation, and temperature range. 



Part II describes how catch and catch-per-unit-effort (CPUE) are related to temperature. A series of weekly 

 airborne temperature surveys were flown over a high catch rate area off San Diego, Calif. , April through October, in 

 1972, 1973, and 1974. These temperature data were compared with catches of yellowtail. Pacific barracuda, and 

 Pacific bonito by the sportfishing fleet within the survey area. Graphical Kolmogorov-Smirnov cumulative prefer- 

 ence curves of catch versus temperature for yellowtail. Pacific barracuda, and Pacific bonito show increased catch 

 rates through the midrange temperatures 17.8° to 20.0°C (64° to 68°F) with a reduction in rates above 20.5°C 

 (69°F). 



Fora31-wkperiod starting on 1 April 1972, 1973, and 1974, the temperature at the 20th percentile of the catch 

 temperature curve was slightly above the 20th percentile of the cumulative temperature curve, indicating that fewer 

 fish were taken at the very lowest temperatures; otherwise, catch for the three species appears representative of the 

 temperature distribution. The average yearly temperature for large catches of Pacific barracuda, yellowtail, and 

 Pacific bonito (30 % or more above mean) fluctuated from 1 6.2 °C (6 1 .2 °F) to 23 .0°C (73 .5 °F) , with a mean value of 

 19.5°C (67.1°F) for Pacific barracuda, 18.5°C (65.4°F) for yellowtail, and 19.6°C (67.4°F) for Pacific bonito. 

 Nonparametric rank correlation tests {Spearman and Kendall) for catch and CPUE versus temperature showed consis- 

 tently higher correlations for catch than for CPUE, indicating an increase in effort with increasing catch. In analyses 

 of temperature and CPUE by species and year for 12-, 17-, and 3 1-wk periods, about one-half of the individual cases 

 tested were, on the average, statistically significant at the .05 level. 



Temperature distributions within 20th percentile ranges of the cumulative CPUE curves obtained for the three 

 species combined indicate that the lowest temperature range, 12.7° to 15.5°C (55° to 60°F), is the only area where 

 catch rates were lower than expected. 



There is little evidence for a preferred temperature within the range of 15.5° to 21.1 °C (60° to 70°F). Conclu- 

 sions from this study indicate that fishery data are by no means optimal for examining the hypothesis of preferred 

 temperature, due to confounding of cause and effect between catch and effort. Lack of simultaneous observation of 

 the spatial distribution of species and environmental measurements over the extent of distribution over time are limit- 

 ing factors in determining the true relationship of species to the environmental factor of sea surface temperature . 



INTRODUCTION 



Normal and anomalous changes in the ocean environment, as mea- 

 sured by sea surface temperature (hereafter referred to as "tempera- 

 ture"), produce a variety of effects upon the apparent abundance and 

 geographical distribution of coastal and oceanic pelagic marine spe- 

 cies. The coastal marine environment consists of biological, chemi- 

 cal, and physical factors which may independently, or in 

 combination, influence the abundance and distribution of fishery 

 resources. Although temperature is a commonly observed environ- 

 mental variable, only limited statistical information is available com- 

 paring the catch of fish in waters of different temperature. A recent 

 comparative temperature study in the northeast Pacific was prepared 

 by Radovich (1975). 



Development of management programs for coastal pelagic fish- 

 eries requires knowledge of the distribution of pelagic species, with 

 regard to natural fluctuations in the physical marine environment. It 

 may be possible to use environmental information to improve esti- 



1 Southwest Fisheries Center La Jolla Laboratory, National Marine Fisheries 

 Service, NOAA. PO. Box 271. La Jolla. CA 92038. 



mates of population size and distribution, and to evaluate the effect of 

 environmental changes on catch. However, in order to apply fully 

 effective resource management, we must learn more about how 

 coastal species respond to changes in their environment. 



Temperature is one physical variable which is relatively easy to 

 measure. The oceans surface layer temperature reflects the exchange 

 of thermal energy from solar, atmospheric, and subsurface sources. 

 The relationship between temperature and the distribution and migra- 

 tion of marine and anadromous fishes has long interested researchers. 

 Along the west coast of the United States and Canada during years of 

 unusually warm surface water, pelagic species common to the lower 

 latitudes in the northeast Pacific have been recorded far north of their 

 normal range, and, in some cases, changes in coastal migratory pat- 

 terns have been recorded (Hubbs and Schultz 1929; Walford 1931; 

 Radovich 1961; Royal and Tully 1961). Since a relationship exists 

 between anomalous temperature and the occurrence of pelagic spe- 

 cies, temperature may provide a means of predicting, within seasonal 

 and statistical limits, the occurrence or distribution of coastal marine 

 and anadromous species. The objective of this study was to define the 

 relationships between catch (as a measure of apparent abundance), 

 and temperature, for selected species in different geographical and 

 environmental areas. 



