FAHAY: OCCURRENCE OF SILVER HAKE EGGS AND LARVAE 



Figure 2. — Gulf V high-speed plankton sampler with depressor. 



aperture size of 0.52 mm (0.02 inch). Other 

 dimensions are as described by Arnold (1959). 



Our method of towing tw^o samplers consecu- 

 tively was described in detail in Clark et al. 

 (1969), Richards and Kendall (1973), and Smith 

 (1973). Figure 3 illustrates schematically our 

 towing methods over various depths of water. As 

 illustrated in Figure 3, the step-oblique method 

 sometimes resulted in unequal sampling intensity 

 at certain depths under a unit of surface area. 

 Therefore, to diagram the horizontal distribution 

 on maps, I combined the catch of the two nets and 

 adjusted them as shown in Table 1. 



The catches of the two nets presented separately 

 provide added useful information. This is especial- 

 ly true in view of 1) observed differences in num- 

 bers and length-frequencies between the catches 

 of the two nets, and 2) the presence of a thermo- 

 cline within the stratum sampled by the deep net. 

 In Appendix Table 1, I tabulated the catch of the 

 deep net as observed. However, the deep net was 

 not equipped with a closing device and was sub- 

 ject to contamination in the upper 15 m during 

 setting out and hauling back procedures. There- 

 fore, for study of vertical distribution, I adjusted 

 the deep net catch after assuming that it sampled 

 the upper zone for 3 min. 



Tows are labeled "D" (day), "N" (night), or "C" 

 (crepuscular, i.e. within 1 h of sunrise or sunset) 

 in Appendix Table 1. 



After each tow, we washed the samplers down, 

 removed the cups, and preserved the samples in 

 buffered 5% Formalin. The samples were returned 

 to the laboratory where all ichthyoplankton was 

 removed and larvae divided into family groups. 

 Gadids and merlucciids were then identified to 

 species. Eggs were initially grouped according to 

 their diameters. Early silver hake eggs are indis- 

 tinguishable from the eggs of many other species 

 of marine fishes. Common characteristics include: 

 outside diameter of about 1.0 mm, presence of a 

 single oil globule, narrow perivitelline space, and 

 4:1 ratio of egg diameter to oil globule diameter. 

 Consequently, specific identifications were 

 limited to eggs in advanced stages of development. 

 I based identifications of late stage M. bilinearis 

 eggs on published descriptions (Kuntz and Rad- 

 cliffe, 1917; Sauskan and Serebryakov, 1968) and 

 on my own rearing experiments with artifically 

 fertilized eggs. The purpose of my experiment 

 was to determine whether pigment was present 

 on the yolk. It was terminated before hatching 

 occurred. Prolarval offshore hake, M. albidus, 

 were identified following the descriptions by 

 Marak (1967) and removed from the M. bilinearis 



Table 1. — Method used to combine the catches of shallow and deep samplers. 



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