Between 1993 and 2018, Ireland's catch samplers have sampled 1,560 commercial fishing trips covering numerous fishing grounds including Stanton Bank, back of the Aran Islands and the Smalls. The positions of the hauls from which discards have been sampled are shown on the map on the right.
Scientists collect essential data for fish stock assessments when fishers land their catch. Additionally, sampling at sea allows scientists to quantify the part of the catch that is not landed at the ports. They estimate the amounts of fish that are landed or discarded, and collect age and length data.
The Irish fisheries are very diverse, so we need to sample a large number of fishing trips before we can estimate the amount of fish that are caught. We typically have observers on around 100 fishing trips per year and around carry out 300 to 400 port visits per year. In some fisheries, catch samples are also provided by the fishers themselves. These self-sampling schemes are also a valuable source of data.
By sampling the commercial catches we collect crucial data on the amount of fish that is caught as well as their age and length composition of the fish. Many fish species can be aged; this information allows assessment models to track the abundance of cohorts of fish over time and analyse the age composition of the catch each year. The models use this information to estimate the size of the fish stocks. Recording of by-catch including endangered and protected species is also carried out on these trips.
The catch samplers carry out very valuable work on assessing discard rates in the Irish fleet. They need to go to sea on commercial fishing vessels every month and for this we rely on the co-operation of the fishing industry. Without the support of fishermen this programme could not succeed.