The Catch Number Between Bassetts Mead And Hale Farm
3549 WordsOct 3, 201415 Pages
This study has shown that there are significant differences in the catch number between Bassetts Mead and Hale Farm indicating that there could be a larger population of P. leniusculus at Bassetts Mead. However, it was observed on several occasions that over 100 individuals had been removed from the river at Hale Farm in a night. With this evidence, further investigation using multiple mark recapture (MMR) techniques would be required to categorically state whether there is a higher population at one of the locations. Furthermore, this could indicate that the ARTs do not provide a representative sample of the resident population. However, P. leniusculus resides in crevices and burrows during daylight hours and the ARTs are designed to…show more content…
These include: water temperature, water quality, forage and feeding regime, population density, size and structure, weather patterns and moon phase (Romaire, 1995). Therefore, the ARTs are likely to be the most efficient and effective way of trapping crayfish. There are also significant differences in the catch numbers within the locations at the different ARTs. This shows that there is variability in the distribution of the P. leniusculus populations within the rivers. This could be caused by a number of factors, such as predators, vegetation, light intensity, water depth, temperature and riverbed substrate composition (Englund and Krupa, 2000; Blake et al., 1994; Nyström, 1994 and Blake and Hart, 1993). The research carried out in this study will focus on the latter two.
It was found that the inter- and intrasite sex ratios (1.1M: 1F at Bassetts Mead and 1.33M: 1F at Hale Farm) were not statistically significant; this reveals that there is no dominance by one particular sex. However, it was observed that there were slightly more males than females caught (Fig. 3.2). Primary sex ratios in crustaceans are typically 1:1 reflecting stable chromosome-based sex determination mechanisms. However, both genetic and epigenetic factors (e.g. environment) are known to distort sex ratios in some species and aberrant sex ratios can be produced by interspecific or