AHLSTROM: KIND AND ABUNDANCE OF FISH LARVAE 



Table 11. — Comparison of relative abundance of fish larvae (average number per haul) in the monitoring pat- 

 tern as compared with the total pattern occupied on EASTROPAC II and equivalent EASTROPAC I for more 

 abundant families. 



parison, four were taken in somewhat higher 

 numbers in the monitoring pattern and three 

 in the more extensive ETP I coverage. Among 

 the latter, less than half as many scombrid lar- 

 vae were taken per haul in the smaller pattern 

 as compared with the larger. 



The average abundance of larvae in the mon- 

 itoring pattern on ETP II was only 73.5% as 

 many as for the total ETP II pattern. Larvae 

 of three families were slightly more abundant 

 in the monitoring pattern than in the total ETP 

 II pattern, including Gonostomatidae, Paralepl- 

 didae, and Idiacanthidae; larvae of Scombridae 

 and Nomeidae were about equally abundant in 

 the two patterns. Four families of fishes, how- 

 ever, including Myctophidae and Sternoptich- 

 idae, were less abundant in the monitoring pat- 

 tern as compared with the total ETP II pattern. 

 Caution has to be exercised in the applications 

 made of data from the monitoring pattern alone. 



TEMPORAL CHANGES IN ABUNDANCE 

 IN MONITORING PATTERN 



Data from six successive bimonthly cover- 

 ages of the monitoring patterns are exception- 

 ally useful for determining the annual reproduc- 

 tive cycles of fishes in tropical waters. Data on 

 relative abundance (average number per haul) 

 are summarized for the 10 most common families 



in Table 12 and for selected genera and species 

 in Table 13. The time period covered by each 

 of the six surveys is indicated in these tables, 

 and will be used for identifying cruises in the 

 discussion. 



The first thing to note is the range in abun- 

 dance of total larvae on the six cruises: the high- 

 est abundance, 255.1 larvae per haul (August- 

 September) was slightly less than double the 

 lowest abundance, 133.1 larvae per haul in De- 

 cember-January. Range in abundance of larvae 

 of each of the 10 families during the yearly cycle 

 will be briefly discussed. 



Myctophidae ranked first in all cruises, al- 

 though barely so in the cruise made during June- 

 July. The highest average number of larvae 

 per haul, 116.4, obtained in August-September 

 was almost double the lowest value, 58.7 larvae 

 obtained in December-January. Myctophid lar- 

 vae were as low as 37.9 9r of the total larvae 

 (June-July) , as high as 57.1 ^r (October-Novem- 

 ber), and had an overall percentage contribu- 

 tion of 47.5%. 



Gonostomatidae ranked second in all cruises; 

 the lowest abundance per haul, 32.6 larvae in 

 October-November, was less than half the high- 

 est value, 77.9 larvae per haul in August-Sep- 

 tember. Percentage contribution ranged be- 

 tween 18.5% (October-November) and 37.7% 

 (June-July) and averaged 26.9%. 



Sternoptychidae ranked third in abundance 



1167 



