FISHERY BULLETIN: VOL. 82, NO. 1 



over, there is a firmly held belief that white croaker 

 are unusually wormy. In fact, the frequency of 

 occurrence of nematodes (larval Anisakis and 

 Phocanema) in white croaker muscle is lower than 

 that for at least some other important sport and com- 

 mercial species such as California halibut, 

 Paralichthys californicus, and chilipepper rockfish, 

 Sebastes goodei (Dailey et al. 1981). 



Because white croaker are abundant around sewage 

 outfalls and tolerant of degraded environments, 

 much of the recent research on this species has been 

 pollution-centered. Several published works deal 

 with pesticide levels (Castle and Woods 1972; 

 MacGregor 1972; Stout and Beezhold 1981) and 

 pollution-implicated diseases and abnormalities 

 (Russell and Kotin 1957; Mearns 1974, 1979; 

 Mearns and Sherwood 1977; Sherwood 1978). Five 

 small-scale studies have been conducted on its life 

 history (Issacson 1964, 1967; Goldberg 1976; More- 

 john et al. 1978; Ware 1979) 



This contribution represents a summation of 

 unpublished white croaker data obtained from three 

 sources: a life history and fishery study by Love, 

 ichthyoplankton work by McGowen and Lavenberg, 

 and a trawling survey by Westphal. 



METHODS 



Collection of Juveniles and Adults 



Samples were collected monthly (3-6 per month) 

 from October 1978 to February 1981 with a 7.6 m or 

 4.9 m headrope otter trawl in 15-65 m of water be- 

 tween Palos Verdes and Huntington Beach, Calif. 

 Reduced numbers of white croaker also were collect- 

 ed monthly from April 1979 to September 1981 in 

 Monterey Bay with a 4.9 m otter trawl in 10-60 m of 

 water or were purchased from local fishermen. All of 

 these specimens were frozen for later dissection. 

 After thawing, all fish were measured (total length, 

 fork length, standard length), weighed, sexed, and 

 the gonads were weighed. 



Collection of Depth Preference Data 

 for Adults and Juveniles 



Information on white croaker depth preference was 

 based on data from a trawling program aboard the 

 RV Vantuna . Trawling was conducted at a speed of 2- 

 3 kn for 20 min with a 7.6 m (occasionally 4.9 m) otter 

 trawl having a net of 0.6 cm stretch mesh. From Sep- 

 tember 1972 through December 1980, 18 stations 

 (Fig. 1) were sporadically sampled at 10 depths, 

 although most of the trawling effort was performed at 



depths between 59 and 91 m. After shipboard sort- 

 ing, fishes were measured (board standard length) 

 and discarded. All lengths were converted to total 

 length (TL) using conversion factors based on 

 measurements of 100 white croaker (Table 1). 



TABLE 1. — Conversion factors between standard (SL), fork (FL), 

 and total (TL) lengths (cm), based on measurements of 100 white 

 croaker from southern California. 



SL = 0.442 + 79 TL 

 = 0.379+ 82 FL 



FL = 



0.088 + 96TL 

 0.849+ 1 14 SL 



TL=0892 + 1.19 SL 

 = 0.023+ 1.04 FL 



Techniques for Aging Juveniles and 



Adults 



Sagitta were removed from each side of the head, 

 and the otoliths were cleaned, air dried, and stored in 

 vials. Because whole croaker otoliths are difficult to 

 age, they were sectioned on a Buehler Isomer 5 low 

 speed saw, Otoliths were placed on wood blocks and 

 completely embedded in clear epoxy (Ciba 825 hard- 

 ener and Ciba 6010 resin). Each block with its otolith 

 was emplaced on the saw and a dorsal-ventral 0.05 

 cm wafer was cut through the otolith, using two 

 diamond-edge blades separated by a stainless steel 

 shim. Wafers were stored in water for a few days to 

 soften the epoxy (which was removed), then the 

 wafers were placed in a black-bottomed water glass 

 filled with water and read under a dissecting micro- 

 scope at a magnification of 10X. All otoliths were 

 read twice, about 4 mo apart, by Love. When 

 readings did not agree, the otoliths were read again. 

 The value of two coincident readings was accepted as 

 the best estimate of age. Fifteen percent of all 

 otoliths were unreadable due to a lack of recogniz- 

 able annuli. 



Procedures for Determining 



the Timing of Maturation and 



Reproduction 



We estimated length at first maturity by classifying 

 gonads as immature or mature based on the tech- 

 niques of Bagenal and Braum (1971). Smallermature 

 fish and fish just entering their first mature season 

 become reproductive later in the spawning season. 

 Hence we estimated length at first maturity during 

 the peak spawning period of January, February, and 

 March. To ascertain spawning season duration and 

 its relation to body size, we sampled at least 150 

 females/mo in 1 cm size intervals throughout the 



'Reference to trade names does not imply endorsement by the 

 National Marine Fisheries Service, NOAA. 



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