PERCENTAGE OF STARVING NORTHERN ANCHOVY, 



ENGRAULIS MORDAX, LARVAE IN THE SEA AS 



ESTIMATED BY HISTOLOGICAL METHODS 



Charles P. O'Connelli 



ABSTRACT 



The proportion of starving larvae of northern anchovy, Engraulis mordax, was estimated for the 

 Southern California Bight in March 1977 from histological examination of larvae for 64 1 m net tow 

 samples. The number of larvae in the tows varied from to about 400. Approximately 6 per tow were 

 sectioned and examined with the light microscope. Twenty-six specimens were identified as emaciated 

 from anomalies of the trunk musculature and digestive tract. Some of the emaciated larvae occurred as 

 isolated cases at widely scattered locations, but most were from a few nearshore tows, indicating 

 "patches" of starving larvae. Temperature and plankton volume data indicate that the patches were 

 associated with fluctuating environmental conditions. The samples indicate that about 8% of northern 

 anchovy larvae in the Southern California Bight were starving. 



One of the goals in investigations of pelagic 

 fish stocks is that of predicting how large year 

 classes will be at the time they are recruited to the 

 fishery. One of the primary approaches to this 

 problem has been the estimation of larval mortal- 

 ity rates based on abundance estimates from egg 

 and larval surveys. While such surveys will prob- 

 ably continue to be the most reliable source of 

 information on abundance at early ages, the high 

 costs and time delays in processing samples are 

 reasons for seeking alternative approaches 

 (Hunter 1976b). Recently, Lasker (1975, in press) 

 has developed a promising index based on avail- 

 ability of food in concentrations suitable for survi- 

 val of early feeding stages of the northern anchovy, 

 Engraulis mordax. 



This study reports another approach that could 

 provide an independent prediction of year class 

 strength for the northern anchovy; namely, esti- 

 mation by histological methods of the proportion 

 of larvae in the sea showing symptoms of starva- 

 tion. Since level of mortality in a population is 

 likely to be some function of the proportion of 

 larvae observed to be starving, the proportion, if 

 based on adequate sampling, could be an indicator 

 of ultimate year class success. 



Condition factor (Blaxter 1971), chemical indi- 

 ces (Ehrlich 1974), morphometric analyses (Shel- 

 bourne 1957; Nakai et al. 1969; Ehrlich et al. 1976; 



Theilacker 1978), and histological analyses 

 (Umeda and Ochiai 1975; O'Connell 1976; 

 Theilacker 1978) have all been used with some 

 success to chai'acterize the starving condition in 

 larvae of various marine species, in most cases 

 under controlled laboratory conditions. The his- 

 tological approach differs from the others in that 

 the criteria of starvation are based on qualitative 

 changes in the character of cells and tissues, not on 

 quantitative measurements. Histological criteria 

 developed earlier for northern anchovy larvae 

 starved in the laboratory (O'Connell 1976) were 

 the principal guidelines for evaluating the condi- 

 tion of ocean-caught larvae in this study. 



METHODS 



In March 1977, 64 net tows were taken over a 

 12-d period from the NOAA ship David Starr Jor- 

 dan to obtain northern anchovy larvae for his- 

 tological study. Almost half of the tows were taken 

 between 2 and 10 mi (3.7-18.5 km) from the coast, 

 most were near Newport Beach, Calif., where 

 northern anchovy eggs and larvae were abundant, 

 but some were much farther offshore. A surface 

 temperature was taken by bucket thermometer at 

 each net tow station. 



Net tows were taken with aim plankton net on 

 which the cod end was a cylindrical Plexiglas^ 



'Southwest Fisheries Center La Jolla Laboratory, National 

 Marine Fisheries Service, NOAA, P.O. Box 271, La Jolla, CA 

 92038. 



Manuscript accepted October 1979. 

 FISHERY BULLETIN: VOL. 78, NO. 2, 1980. 



^Reference to trade names does not imply endorsement by the 

 National Marine Fisheries Service, NOAA. 



475 



