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A Study of Syngnathus scovelli in Fresh Waters of Louisiana and Salt Waters of Mississippi

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A breeding population of Syngnathus scovelli was discovered in 1960 in Lake St. John near Ferriday, Louisiana, which is over 300 river miles from the Gulf of Mexico by the shortest possible route. Although S. scovelli has been known to be euryhaline, this constitutes the first record of a breeding population in fresh water.

This study encompassed the period from July 1960 through February 1966. During this time S. scovelli were maintained for varying periods of time in fresh water aquaria. The longest period of time any one specimen lived in captivity was from 29 September 1960 until 16 November 1962, almost 27 months. The chief limiting factor to the maintenance of S. scovelli in fresh water aquaria appears to be a ready supply of live plankton for food.

The breeding process of brackish water specimens was observed and is described. Gestation took 12 days in two males in August and both males bred the day after giving birth to a previous brood.

Young S. scovelli measured 12 mm at birth. This is the first report of the length of newly born S. scovelli in the literature. A size range of 12-160 mm in length was noted for the species.

A very rapid growth rate has been noted in the young from 12-80 mm, but growth slowed greatly at 80 mm. Three apparent year classes have been postulated among the specimens of S. scovelli collected in Lake St. John. These were: 0 (12-80 mm) , 1 (80-120 mm) , and 2 (120-160 mm) . Consecutive monthly data have not been consistent enough to prove this. Failure to collect these data may be due in great measure to the rotenone placed in Lake St. John by the Louisiana Wild Life and Fisheries Commission on 12 October 1961.

The fresh water population from Lake St. John showed less variation in meristic characters than did the fish from Mississippi Sound.

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