FISHERY BULLETIN: VOL. 75, NO. 1 



Beckman 2 RS5-3 salinometer), and turbidities 

 ranged from 0.2 to 2.8 Formazin turbidity units 

 (determined with a Hach turbidimeter). Substrate 

 was similar to the sand regime (greater than 80% 

 sand) described by Waller (1961). Submergent 

 vegetation was dense in the shallow zone, less 

 dense in the mid zone, and sparse in the deep zone 

 and consisted primarily of turtle grass, Thalassia 

 testudinum; shoal grass, Diplanthera wrightii; 

 and manatee grass, Syringodium filiforme. At 

 least 70 species of fishes and sharks were caught 

 by gill nets in 1973 in the immediate vicinity of the 

 study area (May et al. 1976; Pristas and Trent 3 ). 



The gill nets were constructed of either #208 

 monofilament webbing (transparent; 0.52-mm 

 strand diameter) or #220 multifilament webbing 

 (white; 0.64-mm strand diameter). The 9.5-cm 

 (3%-inch) stretched mesh webbing was hung on 

 the half basis (two lengths of stretched mesh to one 

 length of float line) with the floats spaced 1.5 m 

 apart. The nets were 33.3 m long and either 1.5, 

 3.0, or 6.1 m deep. Nets were held in position by 

 bridle lines attached to anchors. 



One monofilament and one multifilament gill 

 net were set in each depth zone and were about 50 

 m apart. The webbing types were randomly as- 

 signed to the two net locations each time the nets 

 were set. The nets were fished during eight periods 

 from 19 September to 29 December 1972 (Table 1) 

 and were set and pulled within ±1 h of sunset 

 during each period. Nets were fished in a random 

 order and removal of fish from the nets required 

 from 1 to 3 h. Night catches were removed from the 

 nets between 1 h before to 2 h after sunrise, and 

 day catches were removed within ± 1 h of sunset; 

 consequently, day and night fishing intervals 

 overlapped slightly. 



Wilcoxon's signed rank test, a nonparametric 

 procedure, was used statistically to compare catch 

 per net between day and night and between 

 monofilament and multifilament samples. For 

 these comparisons the number of fish of a species 

 caught in a single net, categorized by webbing 

 type, depth zone, and day or night was used. 



Tukey's if -procedure was used statistically to 

 compare catch per net between depth zones. For 

 this procedure, the number of fish of a species 

 caught per net per 24-h period was transformed 



2 Reference to trade names does not imply endorsement by the 

 National Marine Fisheries Service, NOAA. 



3 Pristas, P. J., and L. Trent. 1976. Seasonal abundance, size, 

 and sex ratio of fishes caught with gill nets in St. Andrew Bay, 

 Florida. (Unpubl. manuscr.) 



(log 10 number caught + 1) prior to running the 

 comparisons. Comparisons within each webbing 

 type and time of day were not made because of 

 insufficient data. Both testing procedures are 

 described by Steel and Torrie (1960). 



In our comparisons between depth zones a 

 question arose as to whether the catches should be 

 adjusted for the unequal amounts of webbing 

 fished among depths, i.e., the 1.5-m nets had half 

 and a fourth as much webbing as the 3.0- and 

 6.1-m nets, respectively. We did not adjust values, 

 because we were interested in the number of fish 

 passing over an area of bay bottom per unit time 

 (i.e., the depth at which the most fish could be 

 caught) rather than the number of fish passing 

 through a unit volume of water per unit time. On 

 this basis we did not need to adjust catches among 

 depths, because each net blocked the same 

 horizontal distance of the water column. 



Intermittently, the nets were inspected for 

 damage. Damaged areas never exceeded 8% of the 

 total net area before the netting was repaired or 

 replaced. 



RESULTS 



During the study, 4,066 fish representing 30 

 families, 52 species, and 1 hybrid were caught. We 

 decided that catches of only the 12 most abundant 

 species provided sufficient data for comparison. 

 These 12 species composed 92% of the total catch 

 (Table 1). Of the 12 species, 4 (bluefish, Pomato- 

 mus saltatrix; Spanish mackerel, Scomberomorus 

 maculatus; Atlantic croaker, Micropogon un- 

 dulatus; striped mullet, Mugil cephalus) are 

 considered important locally as recreational and 

 food fishes. The other eight species were: Gulf 

 menhaden, Brevoortia patronus; sea catfish, Arius 

 felis; yellowfin menhaden, B. smithi; little tunny, 

 Euthynnus alletteratus; Atlantic sharpnose shark, 

 Rhizoprionodon terraenovae; gafftopsail catfish, 

 Bagre marinus; hybrid menhaden, Brevoortia 

 patronus x B. smithi (Reintjes 1969); and pinfish, 

 Lagodon rhomboides. 



Comparisons Between Webbing Materials 



Differences in catch per net between webbing 

 materials varied in relation to species, time of day, 

 and depth zone. Combined (times of day and 

 depths) mean catches in monofilament webbing 

 were significantly greater than those in mul- 

 tifilament webbing for Gulf menhaden, bluefish, 



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