TRENT and PRISTAS: SELECTIVITY OF GILL NETS 



TABLE 2.— Continued. 



mesh-size pairs for blue runner and in the 7.6/7.0 

 cm mesh-size pair for Atlantic croaker. Spot, 

 pigfish, and Atlantic croaker were almost always 

 caught wedged tightly in the meshes of gill nets. 

 Blue runner were also usually caught in this 

 manner. Occasionally, however, blue runner were 

 caught by the dorsal antrorse spine which hooks 

 over one or more bars of the mesh or meshes. If the 

 spine were not present, these fish could pass 

 through the meshes. Blue runner caught in this 

 manner probably contributed greatly to the 

 variation about regression. 



Acceptable fits of the data, at least for most 

 mesh-size pairs, were obtained for gulf and 



yellowfin menhaden. The normal curve, although 

 acceptable, did not appear to be the most ap- 

 propriate model to describe selectivity for gulf and 

 yellowfin menhaden because of observed cur- 

 vilinearity. Values of s yx were smallest for gulf 

 menhaden in the mesh-size pairs (8.2/7.6, 8.9/8.2 

 cm; Table 2) that did not exhibit strong cur- 

 vilinearity. Gulf and yellowfin menhaden were 

 usually caught tightly wedged in the meshes at or 

 near maximum girth, but occasionally the larger 

 individuals taken from a particular mesh size 

 were caught loosely in a mesh by the opercle or 

 preopercle. The slight positive skews observed in 

 the length-frequency distributions (Appendix 



191 



