Mexico. Samples were taken both day and night on ebbtides from 18 May to 1 

 August 1966. 



Brovm shrimp were caught throughout the sampling period. Two peaks 

 occurred — one in May and one in June. Estimates of the mean catch per unit 

 effort indicated that the shrimp were near the surface at night and near the 

 bottom during the day. 



The mean lengths of the brown shrimp taken during the day and night with 

 bottom and surface trawls in the same sampling date were similar. The size of 

 the emigrating shrimp increased significantly as the season progressed. 



177. TRENT, W.L., PULLEN, E.J., and MOORE, D., "Waterfront Housing Developments: 

 Their Effects on the Ecology of a Texas Estuarine Area," Fishing News^ Ltd.^ 

 Marine Pollution and Sea Life, Dec. 1972. 



Studies were conducted during 1969 to compare the ecology of a natural 

 estuarine area (marsh and bay) with the ecology of an adjacent estuarine area 

 altered by channelization, bulkheading, and filling. In each area, hydrographic 

 factors, fishes, crustaceans, and benthic macroinvertebrates were sampled period- 

 ically from March to October. Setting, growth, and mortality rates of juvenile 

 oysters {Crassostrea virginiea) were measured from February to October, and 

 phytoplankton productivity was determined from June to August. 



Values of oxygen, nitrite, and kjeldahl nitrogen were significantly 

 higher in the natural area; total phosphorus was significantly higher in the 

 altered area. Although 64 species of fishes and crustaceans were collected 

 by trawl, 6 species comprised 88.8 percent of the total catch. Brevoortia 

 patronus, Anchoa mitahitli, and Micvopogon undulatus were most abundant in the 

 altered area; Penaeus azteaus, P. setiferus, and Leiostornus xanthurus were 

 most abundant in the natural area. The setting rate of oyster spat was 14 times, 

 and the rate of growth of juvenile oysters was 1.8 times, greater in the natural 

 than in the altered area. Oyster mortality was significantly greater in the 

 altered area during the summer. 



Gross production of phytoplankton in the surface waters averaged 2.24, 

 2.06, and 1.17 milligrams of carbon per liter per day in the altered, marsh, 

 and bay areas, respectively. In part of the altered area, extremely high 

 phytoplankton production, which caused low dissolved oxygen, reduced the abun- 

 dance of fishes and invertebrates in the summer. 



178. TRENT, L., PULLEN, E.J., and PROCTOR, R., "Abundance of Macrocrustaceans 

 in a Natural Marsh and a Marsh Altered by Dredging, Bulkheading, and 

 Filling," Fishery Bulletin, Vol. 74, No. 1, Jan. 1976, pp. 195-200. 



Indexes of abundance of macrocrustaceans from March to October 1969 in 

 West Bay, Texas, were determined for day and night and statistically compared 

 between (a) a natural marsh area, (b) upland and bayward canal areas of a hous- 

 ing development, and (c) an open bay area. Significance levels of 5 or 1 percent 

 were used in the statistical comparisons. Catches of brown shrimp, Penaeus 

 azteaus, white shrimp, P. setiferus , blue crab, Callineetes sapidus, and 

 pink shrimp, P. duorarum, were significantly greater at night than during the 

 day at one or more stations in the marsh. More grass shrimp, Palaemonetes sp.. 



56 



