FISHERY BULLETIN: VOL. 78, NO. 2 



bucket (length 30.5 cm, diameter 10 cm) that could 

 be removed quickly. Tows were of short duration 

 to minimize the time larvae would be under stress 

 during capture. The net was let out at a fast steady 

 rate to a depth of 20 m, and then retrieved at a 

 moderate rate. The mean tow time was 3 min (SD 

 = 40 s). 



The net drained rapidly as it was hauled out of 

 the water, leaving the cod end cylinder filled with 

 water containing a light to moderate amount of 

 plankton. The contents of the cylinder were im- 

 mediately poured into a small sieve made of 0.505 

 Nitex mesh netting, and the sieve was then sus- 

 pended in Bouin's fluid to fix the concentrated 

 plankton. The total elapsed time from start of tow, 

 when the plankton net first entered the sea sur- 

 face, to submergence in Bouin's averaged 5 min, 8 

 s (SD = 1 min, 9 s). After the initial fixation, about 

 10 or 15 min, the sample was transferred from the 

 sieve to ajar of fresh Bouin's, and this was replaced 

 by 709c ethyl alcohol 2 or 3 d later. 



In carrying out the above procedure the inside of 

 the plankton net was not washed down after re- 

 trieval until the cod end containing the sample 

 had been removed. After the cod end was removed, 

 the inside of the net was hosed down thoroughly in 

 preparation for the next tow. 



Subsequent to the cruise, all northern anchovy 

 and other fish larvae were sorted out of the sam- 

 ples and counted. From those tows containing only 

 a few northern anchovy larvae, all were set aside 

 for sectioning. From those tows containing many 

 larvae, about half a dozen were chosen for section- 

 ing. The number was approximately doubled for a 

 few samples of special interest, e.g., offshore 

 banks. Specimens were picked at random by put- 

 ting all northern anchovy larvae from a given tow 

 in a shallow, wide-mouth container and re- 

 peatedly dipping with a vial as the contents were 

 swirling slowly. During this procedure small 

 specimens with obvious yolk sacs were rejected 

 because they represented nonfeeding larvae not 

 yet vulnerable to starvation. 



The total number of larvae selected for section- 

 ing was 318. Standard length was measured with 

 an ocular micrometer, then each specimen was 

 imbedded in paraffin, sectioned serially as close to 

 the sagittal plane as feasible, and stained in Har- 

 ris' hematoxylin and eosin-phloxine B. Prior to 

 microscope examination the mounted specimens 

 were put in random order with their identities 

 concealed. 



Histological criteria similar to those diagnostic 



for laboratory starved larvae were readily estab- 

 lished for ocean-caught larvae by preliminary 

 examination of a few dozen (unidentified) speci- 

 mens, after which all ocean-caught larvae were 

 classified as to condition. Under Results, the his- 

 tological indications of condition are described 

 first, and then the classification of larvae is 

 examined in relation to other variables, i.e., stan- 

 dard length, geographical distribution, tempera- 

 ture, and plankton volume. 



RESULTS 



Histological Characteristics of Condition 



O'Connell (1976) found the most noticeable ef- 

 fects of artificial starvation of northern anchovy 

 larvae just beyond yolk absorption (3-5 mm) to be 

 cellular dissociation with loss of zymogen in the 

 pancreas, separation and hyalinization of trunk 

 muscle fibers, and shrinkage of the notochord. In 

 the ocean-caught material examined in the pres- 

 ent study, specimens ranging from 2.5 to 10 mm 

 showed anomalies in the trunk musculature and 

 notochord, and occasionally also in the pancreas, 

 that closely resembled the effects of starvation in 

 the laboratory material. These larvae almost al- 

 ways showed, in addition, certain irregularities in 

 the histology of the foregut and the midgut that 

 were more striking than effects seen in the diges- 

 tive tracts of artificially starved larvae. 



Trunk Musculature 



The trunk musculature in the majority of larvae 

 showed good integrity and texture, forming a 

 compact, solid sheet over the lateral surfaces of the 

 notochord, with evident intermuscular matrix tis- 

 sue and only occasional small separations (Figure 

 1). The notochord in such larvae generally had a 

 smooth profile and was rarely separated from the 

 musculature. In some specimens, however, the 

 muscle fibers were noticeably separated from each 

 other throughout, indicating an anomalous condi- 

 tion. In the more extreme cases (Figure 2) the 

 fibers were widely separated with degraded fibril 

 clarity, and matrix tissue was greatly reduced. In 

 such specimens the notochord was also irregular 

 in profile, imparting a "lumpy" shape to the trunk 

 of the animal as a whole. 



Degraded musculature, of course, might be the 

 result of some process other than starvation. One 

 possibility is capture myopathy, which has been 



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