Abstract

Procambarus clarkii is a North American crayfish introduced into the Lower Guadalquivir in 1974. Since then, this species has altered the functioning and structure of the ecosystems invaded. In order to understand the role of P. clarkii in aquatic ecosystems, it is necessary to acquire a holistic knowledge of their life history and the habitats occupied by them. The objective of this study was to investigate the reproductive phenology and bioenergetics of red swamp crayfish via aerobic standard metabolism (R) and nitrogen excretion (U) rates, and maturity index recorded monthly in the field from 1994 to 1996 at different sites in DNP. In addition, catabolized substrate was estimated via O:N ratio. Many morphometric relationships were calculated. Five stages of ovarian development were distinguished from 0 (rest) to maturation stage III with eggs of 1.1-1.8 mm (immediately prior to spawning). The ovary in stage III is large, orange-brown, very compact, and its weight ranges from 260-600 mg. At ovarian stage IV the gonads are mature but no reproduction occurs. In this stage, the eggs are about 2.9-3.4 mm, the ovary is very large, dark brown and turgid, and its weight ranges from 610-870 mg. Maturity index suggests that final ovarian maturation only occurs in the few days immediately before spawning, and that the spawning process is synchronized among populations and among mature females of each population. Numbers of hatchlings at pleopods ranged from 450 to 550 (4.4 to 5.0 mm carapace length). Timing of juvenile release from pleopods varies greatly (from 10 to 35 days). Data analysis suggested that several factors influence spawning of crayfish at the monitored sites. Major factors are water regime and temperature. Berried females support most of their metabolic needs by catabolizing carbohydrates (overall mean of O:N = 30.39) and to a lesser extent by lipids. Aerobic and excretory metabolism of berried females was lower than metabolism of non-berried animals with similar weight. These results agree with suggestions that the red swamp crayfish is a spontaneous spawning species, which may adjust its reproductive cycle to the timing of flooding.

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