FISHERY BULLETIN: VOL. 70. NO. 3 



lOOi- 



lOOr- 



100 



tr 



UJ 



a. 



01 



UNCORRECTED (nj.ig) 



CORRECTED (n'^^jg 



OOi 



J 1 \ I L 



475 675 875 1075 12.75 14 75 



575 775 975 1175 13 75 1575 



L: (mm) 



10.0 



liJ 



" 1.0 



01 



001 



UNCORRECTED (ni.22) 



CORRECTED (n'j.gg) 



475 6.75 875 1075 1275 1475 



5.75 775 9 75 1175 1375 1575 



Lj (mm) 



Figure 5. — Corrected (n'1,12) and uncorrected (njji2) 

 catches by standard length (Lj) of Pacific sardine taken 

 at night with type 1 (0.55-mm mesh) net. Catches are 

 expressed in percent of total. 



fluencing escapement and implied that the co- 

 efficient of variation of mesh width is greater 

 for silk than nylon nets. The results of this 

 study agree with Heron's conclusions. 



The results indicate that two similar types of 

 sampling gear have greatly different mesh reten- 

 tion properties for anchovy larvae. This implies 

 that considerable care should be taken in the se- 

 lection of sampling gear if quantitative estimates 

 of the abundance of fish larvae are desired. The 

 similarity in mesh retention shown for anchovy 

 and sardine larvae may be due to the fact that 

 the larval forms are very similar. However the 

 diversity of forms found in fish larvae is tre- 

 mendous. Mesh retention should be estimated 

 before quantitative estimates of the relative 



Figure 6. — Corrected (n'ij22) and uncorrected (W1J22) 

 catches by standard length (Lj) of northern anchovy 

 taken during day with type 1 (0.55-mm mesh) net. 

 Catches are expressed in percent of total. 



abundance of larvae of different species of fish 

 are attempted. The results indicate that ade- 

 quate estimates of mesh retention can be made 

 from less than 30 samples containing the desired 

 species of fish larvae. If the mesh retention 

 curve is curvilinear in the region of fish larvae 

 of minimum size, more samples may be neces- 

 sary. 



The reasoning of Hjort (1926) in expecting a 

 critical period in the early life of fish larvae is 

 intuitively pleasing. Hunter (1972) showed ex- 

 perimentally that a much higher density of food 

 organisms is necessary for survival of 4- to 6-mm 

 anchovy than for larger larvae. However, there 

 is no indication of a critical period at the 4- to 

 6-mm sizes in this study, i.e., there are no major 



846 



