O'CONNELL: PERCENTAGE OF STARVING NORTHERN ANCHOVY LARVAE 



ing few days, when the tows with a high incidence 

 of emaciated larvae were taken. 



DISCUSSION 



The most significant result of this study is that 

 northern anchovy larvae showing symptoms in- 

 dicative of starvation were indeed found in the 

 ocean and were thus identified on the basis of their 

 individual appearance. The emaciated condition 

 of these larvae is very similar to that induced in 

 laboratory animals by total food deprivation 

 (O'Connell 1976), which implies that cir- 

 cumstances of insufficient food were responsible 

 for their occurrence in the ocean, especially where 

 samples contained many such larvae, as off New- 

 port Beach. Other causes are possible, and one of 

 the most obvious is discharge from sewage outfalls 

 in the area. However, the discharges are now dif- 

 fused rapidly and in general appear to be harmless 

 and perhaps even beneficial to nearby young and 

 adult fish (Southern California Coastal Water Re- 

 search Project^). 



Zones of insufficient food might well have 

 existed in the Newport Beach area at the time of 

 the survey. The variations in both temperature 

 and plankton volume, which were clearly dynamic 

 in nature, indicate that there was appreciable 

 water mass movement or instability, and such 

 conditions can alter plankton abundance. Lasker 

 (1975, in press) found, for example, that phyto- 

 plankton blooms believed to be advantageous for 

 first feeding anchovy larvae were variously dissi- 

 pated and suppressed as the water column became 

 unstable in turbulent weather and sea conditions. 

 In the present study the time sequence of plankton 

 volume change off Newport Beach shows the pos- 

 sibility that water with relatively low plankton 

 levels and "patches" of emaciated larvae was 

 being replaced by water with greater plankton 

 abundance, in which larvae were also more abun- 

 dant and generally healthy. 



Although the occurrence of zones of insufficient 

 food is a reasonable hypothesis in regard to the 

 "patches" of emaciated larvae off New^jort Beach, 

 it is not a plausible explanation for some of the 

 other samples, where occasional emaciated indi- 

 viduals occurred among abundant healthy larvae. 



^Southern California Coastal Water Research Pro- 

 ject. 1978. The effects of the ocean disposal of municipal 

 waste. Summary Report of the Commission of the Coastal 

 Water Research Project, June 1978, 27 p. Filed at 1500 East 

 Imperial Highway, El Segundo, CA 90245. 



It can only be surmised that in any location, and 

 despite generally good conditions, there will be 

 some instances of starvation through detrimental 

 combinations of genetic constitution, accident, and 

 chance failure to capture food. 



If circumstances of poor food availability are 

 produced by water mass activity, as suggested 

 above for the Newport Beach area, they are likely 

 to be more or less transient phenomena, which 

 raises the question of short-term susceptibility of 

 northern anchovy larvae. Immediately after yolk 

 absorption, northern anchovy larvae will survive 

 only a day or two without food (Lasker et al. 1970), 

 and they will show visible effects before dying 

 (O'Connell 1976). Protein components are quickly 

 affected because early postyolk-sac fish larvae have 

 negligible lipid reserves (Ehrlich 1974), though 

 such reserves obviously increase with growth and 

 become a buffer against insufficient food (Love 

 1974). Even so, northern anchovy larvae of rela- 

 tively large size, 35 mm SL, survived only 2 wk, on 

 the average, after feeding was stopped, and during 

 this period the average lipid content of living larvae 

 was declining while mortality in the population 

 was rising, with smaller individuals dying sooner 

 than larger ones (Hunter 1976a). Since larvae 

 examined in the present survey were appreciably 

 smaller than the above, thus having lower lipid 

 reserves, the signs of emaciation could have re- 

 sulted from relatively few days of insufficient food. 



Most of the larvae showing histological signs of 

 emaciation in this study also showed signs of pre- 

 vious feeding, not by the presence of food residue, 

 but rather by remnants of eosinophilic inclusion 

 bodies in the hindgut mucosa cells. The starvation 

 and previous feeding indications are not incom- 

 patible. Laboratory feeding studies have shown 

 that growth, lipid content, and survival all decline 

 quickly under limited or discontinued feeding 

 (O'Connell and Raymond 1970; Hunter 1976a), 

 and it is probable that histological signs of deterio- 

 ration would also appear quickly, especially in early 

 larval stages. 



If, as proposed by Hjort (1914, 1926), the level of 

 mortality suffered by the early feeding stages of 

 fish populations is a decisive component of the 

 prerecruitment mortality, some measure of that 

 mortality should be a useful indicator of ultimate 

 year class success. The proportion of larvae ob- 

 served to be starving may be one such useful indi- 

 cator: It is directly visible, and it may reflect a 

 substantial part of total daily mortality. Zweifel 

 and Smith (in press) have estimated average daily 



487 



