Abstract
AbstractPond growout of Cherax tenuimanus to two years of age provided data for mean crayfish weight, surviving density and distribution of individual sizes at intervals and final harvest for 12 single year‐class cohorts. Final mean size (47–156 g) was most significantly related to surviving density (4.5–0.7/m2). A hyperbolic model with a harvest date variable accounted for 89% of the variation in mean weight. The biological basis of this model is that the reciprocal of density, i.e., pond area per crayfish, represents food supply for a bottom‐dwelling crayfish. By incorporating the Richards growth function, the hyperbolic model can be more realistically fitted to include the limit to potential size at very low densities. The growth‐density relationship developed after an initial period of 300 days of low growth (to ∼ 10% of final size) and high mortality. Then, mean weight increased rapidly and density stabilized. Final cumulative production (1.401–3,922 kg/ha) and harvest biomass (1,110–2,991 kg/ha) both increased linearly with density. Survival of the total amount of crayfish produced was about 75% at harvest. Although cohort size distributions were positively skewed, the arithmetic mean size employed in the model was very closely and linearly related to the geometric mean of the lognormal distribution, The causal basis and assumptions of the growthdensity model are discussed in relation to resource sharing by individuals and the disproportionate influence of size‐related dominance behaviour.
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.