Information on the Lough Ree Survey
Information on the Lough Ree Survey
Public Information – Prior to the Survey a public meeting was held, in the Hudson Bay Hotel on Thursday the 20th of February (7:00pm), at which the objectives and nature of the survey were outlined in considerable detail. A question and answer session followed. There were no objections raised by any of the anglers or stakeholders present and the survey was positively welcomed by all in attendance. Attendees included lough Ree stakeholders, state agencies and representatives of the local Coarse, Pike and Trout angler interests.
At this meeting IFI requested the assistance of the L. Ree pike anglers to carry out a quantitative estimate of adult pike stocks in L. Ree by monitoring the numbers of tagged and untagged fish caught in their pike competitions next April – the tagged individuals will be tagged and released in the course of the current survey. The returns from this tagging programme will provide useful information on the growth rates of released pike and on their movement patterns within and outside the lake. The local pike anglers indicated that they would be delighted to co-operate.
Why Survey L. Ree?
IFI is aware of major changes in the ecology of many of our freshwaters over the last three decades. As the statutory body charged with the conservation of our waterways they need to stay abreast of the status of fish stocks in all of our major fisheries, including L. Ree. A fish stock survey, using gill nets, is a standard international procedure for carrying out such a census. This same procedure has been used over the last 35 years to survey a majority of our valuable lake fisheries including Loughs’ Corrib, Mask, Carra, Conn, Cullin, Melvin, Sheelin, Derravaragh, Ennell, Owel, Leane and many others.
Survey Timing
Most Irish lake stock surveys have been carried out in late February/early March. To ensure that the results of the L. Ree survey are comparable with the general survey data base it was critical that this exercise be carried out as planned. Fishes are cold blooded animals –their activity level is controlled by water temperatures. By surveying in February/ March catches are limited and 30% to 50% of all fish captured can be released unharmed – sufficient data can still be generated to evaluate the status of stocks.
It is also worth noting that L. Ree would be difficult to survey post April due to the amount of boat traffic experienced on the lake.
Is this time of year not particularly hazardous to pike?
It is known that pike aggregate and spawn at this time of year in most Irish lakes. In many of the large midland lake systems, such as Lough Ree, pike will move out of the main of the lake to spawn on flooded wetlands or even grasslands. As such, a considerable proportion of the pike population could be out of the lake proper and out of the range of the gill nets at this time of year.
Are new / alternative fishing methods being explored?
IFI continue to explore new fishing methods that will enable us to quantify the stock levels in our fisheries. Currently, a specialised boat fitted with hydroacoustic apparatus is being trialled. This may, in time, offer an alternative method to gill nets but it will require a considerable amount of research and ground trothing, the latter which will be achieved using gill nets.
IFI is also bring into operation large electrofishing boom boats, which have the capability of catching fish in water to 4 metres deep (and deeper in clear lake situations). This method will complement other lake fishing methods but on its own will not be capable of generating the metrics required to assess the stock status of a large lake system.
Survey Catches relative to Stocks
It must be stressed that this netting exercise is a survey of all fish stock species, not a culling exercise in relation to pike or any other species. IFI are well aware that L. Ree is a valuable “mixed fishery” for Cyprinids, Pike and Trout. Data indicates that the proportion of any species captured in such a survey is usually ≤ 0.1% of the stock of any species present.
Gill nets provide the most effective method for catching pelagic fishes in lakes. The nets are generally set for a period not exceeding 24 hours but commonly are fished overnight. Not all fish that enter gill nets are killed and many can be removed and returned alive to the water. Research conducted within IFI over the years, commonly using tagging methods, has demonstrated that many fish that are released from gill nets survive for long periods and are again available to the angler.
Some fish species (e.g. bream and large hybrids) can be relatively unaffected by gill nets as they become passive once they enter the net. The proportion of fish captured in gill netting operations relative to the stock levels present in a lake is very small (usually ≤ 0.1% of the stock of any species present). Every effort is made by IFI staff to release live fish to the water.
What happens to the fish that are killed?
All fish that fail to survive the gill netting operation will be used for scientific purposes. Each fish will be measured, weighed, aged and have their stomach contents examined. This information will be analysed to provide information on the age cohorts of each fish species present, their relative growth rates, their feeding patterns and other relevant information.
Fish scales will be retained for possible subsequent genetic or other use.
Trout Genetic Survey
Currently a Micro satellite DNA study of trout stocks in all sections of the Shannon Catchment, from Carrickonshannon downstream, is underway. Data compiled in relation to the adult trout stock in L. Ree compiled in the course of this survey will be extremely valuable in relation to understanding the dynamics of trout stocks in the Shannon Catchment.
