EFFECT OF STARVATION ON THE HISTOLOGICAL AND 



MORPHOLOGICAL CHARACTERISTICS OF JACK MACKEREL, 



TRACHURUS SYMMETRICUS, LARVAE 



Gail H. Theilacker^ 



ABSTRACT 



Histological and morphological criteria were developed to assess the nutritional condition of 

 laboratory-reEired jack mackerel, Trachurus symmetricus, larvae. A comparison of the histological 

 features of fed and starved larvae revealed that the digestive tract and its associated glands were the 

 first tissues to be affected by starvation. The extent of cellular deterioration increased with time of 

 starvation. To classify larval condition, histological characteristics of the pancreas and gut were given 

 numerical grades. The histological technique correctly classified 839c of the feeding and starving 

 larvae. 



The morphometric analysis relied upon a stepwise discriminant analysis that used a combination of 

 five measurements (standard length, head length, eye diameter, body depth at the pectoral, and body 

 depth at the anus) to estimate individual larval condition. The morphometric method was as sensitive 

 as the histological examination in determining whether or not a larva was fed or starved. Ultimately, 

 these histological and morphological criteria may be useful for estimating larval survival in the field by 

 assessing the condition of sea-caught larvae. 



Fishery scientists generally agree that observed 

 fluctuations in recruitment of young fish to a fish 

 stock may be the consequence of mortality during 

 the larval stage. Because starvation is probably 

 one of the principal causes of mortality (Hunter 

 1976a), a need exists to develop criteria for detect- 

 ing the incidence of starvation in sea-caught 

 specimens. Several scientists have suggested that 

 the differences in body form between feeding and 

 starving larvae could be used to identify the nutri- 

 tional status of larvae caught in sea surveys. For 

 example, Shelbourne ( 1957) based his assessment 

 of the condition of ocean-caught plaice, 

 Pleuronectes platessa, larvae on their external ap- 

 pearance. Certain morphometric measurements 

 also can be indicative of starvation. A decrease in 

 thickness of the larval fish body has been corre- 

 lated with starvation for several marine and 

 freshwater fish larvae [herring, Clupea harengus, 

 and plaice (Ehrlich et al. 1976); northern anchovy, 

 Engraulis mordax (Arthur 1976); anchovy, E. 

 japonica (Honjo et al. 1959; Nakai et al. 1969); 

 pike, Esox lucius, and carp, Cyprinus carpio (Kos- 

 tomarova 1962)]. Other morphological features 

 (Ehrlich et al. 1976) considered to be indicative of 



'Southwest Fisheries Center La Jolla Laboratory, National 

 Marine Fisheries Service, NOAA, La Jolla, CA 92038. 



Manuscript accepted August 1977. 

 FISHERY BULLETIN: VOL. 76, NO. 2, 1978. 



starvation in herring and plaice were a decrease in 

 the angle of the pectoral girdle, a change in the 

 ratio of the head to eye height (herring only), and a 

 decrease in the relative condition factor. Coinci- 

 dent with morphometric differences caused by 

 starvation, Ehrlich et al. (1976) described his- 

 tological changes in the gut and liver. The his- 

 tological approach was used to classify yellowtail, 

 Seriola quinqueradiata, larvae into "feeding," 

 "semi-feeding," and "starving" groups by Umeda 

 and Ochiai (1975). This technique was also effec- 

 tive for diagnosing starvation in northern an- 

 chovy larvae (O'Connell 1976). In both species, 

 degeneration of cells of digestive organs was the 

 best indicator for identification of starvation. Sev- 

 eral other studies also have correlated starvation 

 in fish larvae with degeneration of the digestive 

 organs, mainly the gut. Kostomarova (1962) de- 

 scribed a retardation in development of the gut in 

 larvae of starved carp and pike and a reduction in 

 the depth of the epithelial cells lining the gut. 

 Reduced gut cell height was also reported for the 

 larvae of starved yellowtail (Umeda and Ochiai 

 1975), herring, and plaice (Ehrlich et al. 1976). 



Morphological criteria are preferable to his- 

 tological ones because they take much less time to 

 determine and require no special preservation 

 techniques. However, histological criteria may be 

 more accurate for classifying individual larva. 



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