FISHERY BULLETIN: VOL. 84. NO. 1 



Los Angeles 



Anacapa 

 Santa Barbara- 

 San Clemente 

 Tanner Bank— o 



San Diego _ 



31* N — 



Figure 1— Location of jack mackerel, Trachurus symmetricus, col- 

 lections off the coast of California. Nearshore stations were at 

 Anacapa, Santa Barbara, and San Clemente Islands and at Tan- 

 ner Bank. The grid of open-ocean stations was 350 km offshore; 

 stations were 4 mi apart. 



samples taken offshore; from to 262 fish were 

 caught per sample (Table 1). Larvae sorted from the 

 samples (n = 445) were counted and five body 

 measurements taken: standard length (SL, tip of up- 

 per jaw to perpendicular at end of notochord); head 

 length (HL, tip of upper jaw to cleithrum); eye 

 diameter (ED); body depth at the pectoral (BD-1); 

 and body depth at the anus (BD-2). After measure- 

 ment, some larvae (n = 369) were prepared for 

 histological examination. When samples contained 

 fewer than 50 jack mackerel, most larvae were ex- 

 amined, but when samples contained more than 100 



jack mackerel, about 25% of the fish were examined 

 histologically. Jack mackerel size distribution in the 

 offshore study area (determined for 400 fish taken 

 from stations 16, 23, 34, and 35) was similar among 

 stations and ranged between 2.6 and 4.7 mm SL. lb 

 ensure analysis of all ages in the larger samples, fish 

 were taken equally from each of four length classes: 

 <3.0; 3.0-<3.5; 3.5-<4.0; 4.0-<5.0 mm. These larvae 

 were imbedded in paraffin, sectioned at 6 pm, and 

 stained with Harris hematoxylin and eosinphloxine 

 B (Theilacker 1978). In my analysis of histological 

 data I combined the first two size classes because 

 the size at first feeding was 3.2 mm. 



The prevalence of starvation was assessed for 371 

 jack mackerel selected from 20 of the 32 positive sta- 

 tions (Table 1). In addition, I analyzed 41 jack 

 mackerel taken in 14 hauls from the inshore stations 

 near the Channel Islands and Tanner Bank. 



Histological Analysis 



The histological assessment of nutritional state is 

 based on distinct cellular changes that occur in 

 tissues when larval jack mackerel were deprived of 

 food; these changes are well documented by Umeda 

 and Ochiai (1975), O'Connell (1976), and Theilacker 

 (1978). Tb determine the condition of individual 

 ocean-caught jack mackerel, I used the histological 

 criteria I developed in the laboratory by starving jack 

 mackerel except I did not grade the pancreas. Grades 

 were assigned to 11 histological characteristics of 

 the brain, digestive tract, liver, and musculature 

 (Theilacker 1978, 1981). Fish identities were 

 unknown during this examination. I classified jack 

 mackerel larvae into four categories (healthy, 

 recovering, starving, and dying) according to their 

 histological scores (the summation of the grades for 

 each of the 11 histological characteristics). 



Tissues of jack mackerel from the sea which had 

 tissues similar in appearance to the tissues of 

 feeding, laboratory-raised fish were classified as 

 healthy; sea-caught jack mackerel which resembled 

 laboratory fish that had fasted before eating were 

 classified as recovering (these fish showed signs of 

 feeding and digestion, but also showed signs of star- 

 vation); sea-caught larvae which were classified as 

 starving resembled larvae that had been starved in 

 the laboratory for 1-3 d (Theilacker 1978, 1981). I 

 did not observe the dying category in laboratory- 

 starved larvae; this category is described in Results. 



Morphological Analysis 



Tb detect starvation I used a set of morphological 



