SMITH ET AL.: MORTALITY RATES OF SARDINE AND ANCHOVY EGGS OFF PERU 



Table 2. — Mean number of Peruvian anchovy, Engraulis 

 hngens. and Pacific sardine, Sardinops sagax. eggs per 

 station by age group. The age group code A1 refers to 

 eggs aged in the first half of the first day after spawning; 

 A2 refers to eggs aged in the second half of the first day; 

 B1 refers to eggs aged in the first half of the second day; 

 and B2 refers toe ggs aged in the second half of the 

 second day. "All" refers to all stations where that species' 

 eggs were present. Only the inshore regions (IIVIAR11. 

 IMAR 21 , IMAR31 ) combined were considered for estima- 

 tion of these parameters. "Both" refers to those stations 

 where eggs of both species were present. "Only" refers to 

 stations where that species' eggs were present. 



the small-scale spatial distribution of Pacific sar- 

 dine and Peruvian anchovy eggs was indistin- 

 guishable from total independence of each other. 

 In summary, the results of this study show 

 that Pacific sardines and Peruvian anchovies 

 spawned along the coast over the latitudinal ex- 

 tent of northern and central Peru with the pre- 

 ponderance of spawning within 30 nmi of the 

 coast. The production rate of Peruvian anchovy 

 eggs per unit area (104 eggs/0.05 m" d~^ was 

 about double that for Pacific sardine (56 eggs/ 

 0.05 m^ d"^) and the mortahty rate of Peru- 

 vian anchovy eggs (z = -1.12 or 67% d~^) 

 was substantially lower than that of Pacific sar- 

 dine {z = -2.12 or 88% d"M. The highest 

 mortality rate for both species occurred in the 

 northern region (IMARll). For the Pacific sar- 

 dine in the northern region, the instantaneous 

 rate was -3.88 (98% d"'). For the Peruvian 

 anchovy in the north, the instantaneous rate was 

 -2.14 or 88% d"'. Mortality rates of Peru- 



3). Peruvian anchovy egg production was rela- 

 tively even in all sectors of the inshore region. 

 The mortality rates of both Pacific sardine and 

 Peruvian anchovy were highest in the northern 

 region. Pacific sardine mortality rates were 

 higher than Peruvian anchovy mortality rates in 

 each region. 



Mortality rates of Peruvian anchovy and Pa- 

 cific sardine eggs were not higher where the 

 eggs occurred in the same samples (Table 4). 

 Pacific sardine egg production, in areas where 

 Pacific sardine eggs were not accompanied by 

 Peruvian anchovy eggs in a sample, was only a 

 third of that where the two species' eggs were 

 found together. As in the case of abundance, 

 Peruvian anchovy egg production and mortality 

 rates do not appear to be related to the presence 

 of Pacific sardine eggs in the sample. 



The spatial overlap of the Pacific sardine 

 spawning areas and Peruvian anchovy spawning 

 areas cannot be distinguished from randomness. 

 The probabihty that a 0.05 m" sampler will miss 

 a Peruvian anchovy egg patch was 0.47 and for a 

 Pacific sardine egg was 0.61 in August-Sep- 

 tember of 1981 off northern and central Peru. 

 The joint probability of a sampler of this size 

 missing both species' eggs as estimated from the 

 product of the individual species' probabilities 

 was 0.29. The measured probability of missing 

 both species was 0.28 (Table 1). Therefore based 

 on occurrence in a 0.05 m~ mouth area sampler, 



Table 3. — Regional egg production (Pq) and mortality 

 rates (Z) of Pacific sardine and Peruvian anchovy as esti- 

 mated by a nonlinear least squares procedure assuming 

 an exponential model. 



Species Category 



Production (SE) 

 eggs/0.05 m^.'d 



Mortality (SE) 



daily 

 instantaneous 



Table 4. — Egg production (Pq) and mortality rates (Z) of 

 Pacific sardine and Peruvian anchovy for all inshore re- 

 gions where samples are positive for either species. "All" 

 refers to all stations where eggs of that species were 

 present. "Only" refers to stations which were positive for 

 one species but the eggs of the other species were ab- 

 sent. "Both" refers to stations where eggs of both species 

 were present. 



Species Category 



Production (SE) 

 eggs/0.05 m^/d 



Mortality (SE) 



daily 

 instantaneous 



Sardine 



Anchovy 



501 



