WICKHAM and RUSSELL: EVALUATION OF MID-WATER ARTIFICIAL STRUCTURES 



Table 2. — Diver estimates, purse seiner captain's estimates, and fish house landing totals for daily catches from artificial 



structures. 



Data not used for scuba-diver estimates-purse seiner catch comparisons. 



species attracted to the structures. They were 

 not, however, able to determine accurately the 

 pei'cent species composition for the schools of 

 mixed coastal pelagic fishes. These mixed 

 schools contributed over 95% of the catch weight 

 taken from each structure. The mixed coastal 

 pelagic school fish consisted of round scad 

 (Decapterns pioictatus) and Spanish sardine 

 (Sardiitella anchovia). The bait fish occurred at 

 each structure in mixed schools of varying per- 

 cent species composition. The difficulty encoun- 

 tered by the divers in obtaining accurate percent 

 species composition data for this group was 

 probably the result of behavioral differences " 

 between the species. Round scad usually 

 approached closer to the divers than Spanish 

 sardine, which tended to concentrate on the side 

 of the school farthest away from the divers. 



Jacks usually represented less than 5% of the 

 total catch weight and consisted primarily of 

 small 15-cm (6-inch) blue runner {Caranx 

 crysos), crevalle jack (C. hippos), and bar jack 

 (C. ruber). Among the species which comprised 

 the major components of Klima and Wickham's 

 (1971) jack group, amberjack {Seriola sp.) were 

 only occasionally observed and rainbow runner 

 {Elagatis bipi)i)iulata) were notable by their 

 absence in this series of experiments. The jacks 

 are not treated separately' in our paper because 

 of their minor contribution to the total number 

 and weight of the structure-attracted fish aggre- 

 gations. 



Comparison of diver estimates and purse 



seine catch data indicates that although purse 

 seine data are quantitatively superior both 

 sampling techniques are complementary and, 

 combined, provide a more complete picture of 

 the experimental environment than either singu- 

 larly. Where diver estimates provided the only 

 available data they are considered sufficient to 

 permit rough evaluation of the experimental 

 results in terms of their commercial significance. 



FISH HOUSE LANDING (pounds) 



leOO ZZX 2700 3150 3600 



Figure 3. — Relationship between the daily total of the 

 Gulf Ranger captain's estimates of structure-purse seine 

 catches and the daily fish house landing records. Statistical 

 evaluation of this data by linear regression analysis yields 

 Y = 216.4 + O.S16X\ r- = 0.97. N = number of set es- 

 timates in each daily total. 



185 



