Fish ageing and growth rate analysis
The A.G.A Group was instructed by a Client in Kent to carry out an aging report for selected species after suspicions that things were out of balance. The A.G.A Group visited the fishery during a match and at the end weighed and measured a representative sample from the lake, fish scales were removed for the purpose of aging. After analysis it was discovered that the fish were growing at slower than average rates compared to national averages.
Fish growth rates can slow for a number of reasons (primarily environmental) and it is important to understand that slow growth can be attributed to either a single parameter or a number of factors combined. Stillwater fisheries are often overstocked, whilst initially this could not be said it was the case that given the nature of the mixed stocking that competition between individual populations may have been having a detrimental effect on fish health through increased stress levels.
Factors to consider:
- Inter/intra fish competition
- Water quality
- Over stocking
- Fish health
As such the A.G.A Group recommended that information was obtained to assess stock levels against the ability of the water to carry the biomass that was present. The remedial actions available centred on improving environmental conditions such as increasing marginal vegetation to support the biomass of the lake by providing nutrition for the fish. It was also recommended that the species mixing was reduced to ease inter species competition. By understanding the needs of the fish and improving conditions below the water-line the lake may return to a more natural state with the correct prey/predator hierarchies in place.