The Shimna River is a small coastal catchment in Northern Ireland with a locally significant sea trout (Salmo trutta L.) fishery. A salmonid monitoring programme was initiated on the system in 2002. Cross correlation analysis of 0+ recruitment and survival against a range of potential biological and environmental explanatory factors indicated that low survival was associated with high spring discharge conditions. A significant negative relationship was also evident between 0+ trout survival and both sea trout rod catch and CPUE in the previous year, indicating lower relative survival following high ova deposition years and suggestive of functional density dependent regulation. Further analysis showed a stock-recruitment relationship between both the Shimna sea trout rod catch and CPUE and resultant 0+ fry recruitment. The Ricker model produced the best fit and explained 63% and 70% of the variance in recruitment when plotted against rod catch and CPUE respectively. The recruitment potential of late summer 0+ trout on the Shimna (above the fish counter station) was modelled using electric fishing and habitat data and ranged between 15,830 – 17,908 fish; which corresponded to an estimated ova deposition requirement of 175,890 – 596,926 ova or 3.3 – 11.2 ova m-2 of the total available habitat. The potential ova contribution from the resident brown trout and the sea run component of the stock was estimated; with the majority (> 85%) of the annual ova deposition contributed by ≥1 sea winter sea trout. Larger mature sea run trout are particularly important for the viability of the Shimna stock and the potential implications for future management practices are considered.
|Title of host publication||Sea Trout: Science and Management|
|Subtitle of host publication||Proceedings of the 2nd International Sea Trout Symposium|
|Place of Publication||Leicestershire|
|Publisher||Troubador Publishing Ltd.|
|Number of pages||13|
|ISBN (Print)||978 1788035 354|
|Publication status||Published - 2017|