Life History and Ecology of the Freshwater Caridean Shrimp, Palaemonetes paludosus (Gibbes)

Abstract

The life history and ecology of the freshwater caridean shrimp, Palaemonetes paludosus (Gibbes), was determined from monthly collections for 1 year in the Hillsborough River near Tampa, Florida. Numerical abundance increased from May (95.3/m2) to August (662.6/M2) and then decreased to 121.6/M2 by April of the following year. Biomass showed three distinct peaks, the largest occurring in November (49.2 g/m2). Females outnumbered males in all months except January and May. Ovigerous females ranging from 20-40 mm long occurred from early February to mid-October at water temperatures of 18-33 C; percentage of ovigerous females among mature females was highest (56%) in April. Fecundity ranged from 8-85 eggs and increased with length of the female according to the relationship: Log Y = 0.6228 + 0.0294X. Mean brood size and mean size of ovigerous females decreased from the beginning of breeding to June. Mean brood size was lowest in the last month of breeding. The incubation period in the laboratory was 12-14 days at 26-28 C, Growth to maturity (20 mm) took 2-3 months when water temperatures exceeded 26 C and 4-5 months when temperatures were lower. Postspawning mortality occurred from April to October. Longevity was confined to 1 year. Food consisted primarily of algae, vascular plants, detritus and aquatic insects, in decreasing order of importance. INTRODUCTION The grass shrimp, Palaemonetes paludosus (Gibbes), is common in fresh waters E of the Allegheny Mountains, from New Jersey to Florida. It also occurs in Mississippi, Louisiana, Texas and Oklahoma, probably introduced in the latter three states (Holthuis, 1952). In 1958 the species. (supplied by the Florida Game and Fresh Water Fish Commission) was introduced into the lower Colorado River by the California Department of Fish and Game and now is established in various locations (Hayden and Ringo, 1963; St. Amant and Hulquist, 1969; St. Amant and Day, 1972). Palaemonetes paludosus is predominantly a freshwater species but has been reported in brackish (Tabb and Manning, 1961; McGuire, 1961; Rouse, 1969) and salt waters (St. Amant and Hulquist, 1969). Dobkin and Manning (1964) observed survival at salinity of 300/oo (parts per 1000) in the laboratory. Although Dobkin (1963) described the larval development of Palaemonetes paludosus, there are no complete life history studies of the species. Numerous investigations have been published on kadiakensis Rathbun, the other epigean freshwater Palaemonetes in the United States [Meehean, 1936 (as P. paludosa, see Holthuis, 1952; 1 Present address: Department of Biological Science, Florida State University, Tallahassee 32306.