TRENT and PRISTAS: SELECTIVITY OF GILL NETS 

 TABLE 1.— Continued. 



'Caught commercially in gill nets (National Marine Fisheries Service 1974). 



are caught in gill nets increase with an increase in 

 mesh size seemed probable at least over part of the 

 range of mesh sizes, for 20 of the 22 species (Figure 

 1). The two species that did not show a definite 

 increase in mean length with an increase in mesh 

 size were little tunny, Euthynnus alletteratus, and 

 bonnethead shark, Sphyrna tiburo. Of the 22 

 species, none was caught (in numbers where 

 nrrii > 9) in every mesh size. The relation of an 

 increase in mean length for 20 species (little tunny 

 and bonnethead shark excluded) with an increase 

 in mesh size did not hold throughout the range of 

 mesh sizes for gulf menhaden, Brevoortia pat- 

 ronus; sea catfish, Arius felis; pinfish, Lagodon 

 rhomboides; blue runner, Caranx crysos; bluefish, 

 Pomatomus saltatrix; gafftopsail catfish, Bagre 

 marinus; crevalle jack, Caranx hippos; Atlantic 

 sharpnose shark, Rhizoprionodon terraenovae; 

 and yellowfin menhaden, Brevoortia smithi. The 

 primary reason for low catches in some mesh sizes 

 and for length not increasing progressively with 

 increasing mesh size was that the length ranges in 

 the fished populations of many species were not 

 great enough to provide the sizes offish that many 

 of the mesh sizes would efficiently capture. The 

 two species not showing the expected relation 

 usually were entangled or enmeshed in the 

 webbing in an abnormal manner. Most of the little 

 tunny that were caught were too large to deter- 

 mine mean length-mesh size relations in the mesh 



FIGURE 1.— Mean lengths of fishes caught in gill nets of various 



mesh sizes. 



189 



