The diel vertical distribution of copepods off Galveston, Texas.




Allison, T.C.

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Texas A&M University.


A study of the diel (24-hour) vertical distribution of some Gulf of Mexico copepods was undertaken during June, July, September and November, 1963. Collections with a double-net Clarke-Bumpus sampler were taken by a research vessel of the U.S. Fish and Wildlife Service, Bureau of Commercial Fisheries, Galveston, Texas. Two collection sites were selected; Station A in 12 m mear San Luis Pass, Station B in 36.5 m approximately 50 miles south of Galveston. Station A was sampled only in June while Station B was sampled in all four months. Both stations were sampled systematically at four-hour intervals and at three depths (Station A: 2, 4, and 8 m; Station B: 2, 18, and 34 m) for periods varying from 30 hours in June to 44 hours in November. Forty-six species of copepods which could be identified, plus six species identified only to genus and two species identified only to family were taken at the two stations. Eleven species plus one unidentified immature copepod were abundant and present consistently enough to permit diagramming their diel vertical distributions. Three basic distribution patterns were noted. Seven species (Acartia tonsa, Undinula vulgaris, Eucalnaus pileatus, Calocalanus pavo, Calanopia americana, Temora turbinata, Corycaeus amazonicus) showed evidence of a normal diel vertical distribution. One species (Corycaeus subulatus) appeared to have a reverse diel distribution and three species (Paracalanus parvus, Corycaeus clausi, Oithona plumifera and the juveniles) showed evidence of a normal pattern with very short migrations. Seasonal changes in light, temperature and salinity conditions apparently did not affect the diel vertical distribution of any of the copepods in this study. In addition to the data on diel vertical distribution, several observations were made concerning the copepod community. In June, 1963, the abundance and numbers of species were greater at Station B than at the more inshore Station A. The total copepod abundance was at a peak in June and July during the sampling period. The most abundant copepods present were Paracalanus parvus and Temora turbinata. Lucicutia clausi is a new record for the Gulf of Mexico copepod fauna.


133 p., Dissertation


copepods, marine crustaceans, vertical distribution, diurnal variations, double-net Clarke-Bumpus sampler, vertical migrations, abundance