MORSE: CATCHABILITY, GROWTH, AND MORTALITY OF LARVAL FISHES 



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nate at all lengths (« 50% of the total catch) and 

 day catches amount approximately to only 209c 

 of the total. This relationship of catches is unique 

 among the 26 taxa analyzed and is statistically 

 significant (P < 0.01, Table 3). Offshore hake 

 larvae occur mostly at the shelf break in depths 

 > 200 m (Morse et al. 1987). Since the maximum 

 water column depth sampled by the net was 200 

 m, collections of this species may reflect a ver- 

 tical migration pattern into the net sampling 

 ai-ea during twilight as well as visually cued net 

 avoidance. 



The catches of B. glaciale. C. maderensis, 

 Atlantic herring, and rock gunnel, Pholis gun- 

 nelus, reveal some unique characteristics as 

 analyzed by day, night, and twilight. The length 



range for B. glaciale in Figure 4 is 3-11 mm, but 

 the entire range sampled during this study is 

 from 3 to 52 mm. At 12 mm, the length at which 

 metamorphosis occurs (Halliday 1970), this 

 species is virtually absent from all daylight 

 catches (i.e., 3 individuals > 11 mm in 2,201 

 tows) though they are abundant, measuring up 

 to about 25 mm long, in both night and twilight 

 tows. Larvae are most abundant at the offshore 

 extreme of the survey area (Morse et al. 1987), 

 and the average bottom depth where they occur 

 is about 400 m while the maximum tow depth is 

 200 m. Assuming fish begin at metamorphosis, 

 the characteristic vertical migi-ations of juve- 

 niles and adults, this extreme case of net avoid- 

 ance represents the effect of vertical migration 



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