TRENT ET AL.: ABUNDANCE OF MACROCRUSTACEANS IN MARSHES 



caught in sufficient numbers for detailed 

 analyses. 



Brown shrimp was caught in greater numbers 

 during the day in the canal and bay areas and in 

 greater numbers at night in the marsh area ex- 

 cept at station 6 (Table 2). In the canals, day 

 catches were much greater than night catches at 

 the upland canal stations but were only slightly 

 greater than night catches at the bayward canal 

 stations. In the marsh, night catches were sig- 

 nificantly greater than day catches at stations 8 

 and 9, slightly greater than day catches at station 

 7, and less than day catches at station 6. 



White shrimp was caught in greater numbers 

 at night than during the day at all stations except 

 station 5. The differences were statistically sig- 

 nificant at stations 7-9. 



Grass shrimp, Palaemonetes sp., was caught in 

 greater numbers during the day at two of the 

 canal stations and in greater numbers at night at 

 the remaining stations; the differences were not 

 statistically significant, however. 



Blue crab, Callinectes sapidus, was caught in 

 greater numbers during the day at the upland 

 canal stations (significant at station 3) and in 

 greater numbers during the night at the remain- 

 ing stations (statistically significant at stations 

 5-8). 



Pink shrimp, Penae us duorarum, was caught in 

 greater numbers at night than during the day at 

 all stations except station 6. Differences were 

 statistically significant at stations 5 and 8. 



COMPARISONS OF 

 CATCH BETWEEN AREAS 



Statistically significant differences in night 

 catches between areas were observed for four of 

 the five species; day catches were significantly 

 different between areas only for brown and pink 

 shrimps (Table 3). Abundance of brown shrimp 

 during the day was significantly greater in the 

 bayward canal area than in the upland canal and 

 bay areas, whereas at night, brown shrimp were 

 significantly more abundant in the marsh and 

 bayward canal areas than in the other two areas. 

 Catches of white shrimp at night were sig- 

 nificantly greater in the marsh area than in the 

 other three areas. Blue crabs were significantly 

 more abundant at night in the marsh and bay- 

 ward canal than in the bay and upland canal 

 areas. Catches of pink shrimp were significantly 

 greater in the marsh than in the upland canal 

 area during the day and significantly greater in 

 the marsh than in both canal areas at night. 



CATCH RELATED TO 

 DISSOLVED OXYGEN 



Mean dissolved oxygen values and mean catch 

 of each species by date and area are shown in 

 Figure 2. Mean oxygen values in the bajrward 

 canal, marsh, and bay areas were above 3.0 ml/ 

 liter throughout the study except on 1 July in the 

 bayward canal and on 23 September in the 



Table 2. — Comparisons between day and night catches (mean number caught per tow) by species and station 



(paired comparison f-test with 15 df ). 



'Significant at 5% level. 

 "Significant at 1% level. 



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