A little about the fish
Although bass are widespread along the western seaboard of Europe ((Wheeler), 1969) they are recognised to be a species of warmer waters, typically a southern European, Northern African fish. The Wexford fishery is situated in the zone of greatest abundance of bass on the east Irish coast and thus is as close as possible to the supposed centre for the species in the Celtic Sea (Williams, 1974)
From – (Fahy, 1981)
The sea bass is a sub-tropical species at the northern limits of its range in the British Isles. It is more common along the southern coasts of these islands and forms winter aggregations in the Celtic sea from which it disperses around the coast of Britain and Ireland as the water warms in spring and summer. Bass stocks are maintained by variable recruitments which also appear to be temperature related and probably regulated; a succession of good recruitments and improved growth contributing to a build-up of stocks to bring about a cyclical abundance. (Fahy, 2000)
There is no doubt that as we continue to catch bass all along our coasts today and while frequent exceptions occur as regards numbers, timings and even locations, lots of ‘patterns’ remain the same whilst some may be changing. Global warming and its effects will surely play a major role on the movements and populations of the fish in the current and future years.
Devauchelle (Devauchelle, 1984) suggested that gonad maturation and spawning were influenced by temperature; Kelley (1988) believed that exceptionally cold weather was detrimental to bass during their first sea winter. Perhaps the greatest influence that we are experiencing at this time is the possibility of rapidly changing and fluctuating sea temperatures. Pawson (1992) identified critical seasonal temperature periods in the annual biological cycle of bass
- November to the following March when the gonads develop
- March to May when spawning occurs and
- May to November when growth takes place
Temperature conditions on the Irish coast are critical to the performance of bass stocks and as Pawson demonstrated in his paper the seasonal inshore waters of the English Channel had undergone cycles of cooling and warming and cooling during the decade 1980-1990. Data collected at Malin head and expressed in similar fashion over the same period demonstrates similar patterns in temperature fluctaution as experienced in the English Channel.
Pawson demonstrated the correlations between the abundance of juvenile bass in the English Channel and the temperature deviations determined.
Kennedy and Fitzmaurice (Fitzmaurice, 1972) found that it was possible to identify years of both good and poor growth in bass. They also identified that good growth years were successful brood years. Further analysis of the data led to the conclusion that bass in Irish waters conform to a single growth curve which is temporarily altered by either good or poor growing years.
On the further south eastern and southern coasts from (Fitzmaurice, 1972) ‘Adult bass are present in estuaries and along the shore as a rule until late November or even December. Bass have been caught on hand lines in Youghal bay in fine weather in January and the salmon netsmen take occasional bass in the nets in Youghal bay in February and March. In January 1953 a trawler took a large catch of adult bass about 1 mile from Rosslare Harbour and 3.5 miles from Wexford harbour. These bass were caught in 3 fm’s over clean sand in an area of extensive sandbanks. Some bass therefore do not go very far from shore or into deeper water during the winter.’
Kennedy and Fitzmaurice conclude ‘Sea temperatures are probably the main factor influencing the autumn, winter and spring movements of bass.’
With an extremely mild winter of 2011/12 experienced so far and an extremely cold winter of 2010/11 fish will continue to move and perform according to the influences as they have done in the past.