A collaboration between Irish researchers from NUI Galway and Cork Harbour Angling Hub is the first in the world to track the detailed movements of individual sea bass in European waters.
The study, published in Science Reports was co-authored by Dr Tom Doyle, Ryan Institute, NUI Galway in collaboration with researchers Damien Haberlin, Ashley Bennison and Dr Mark Jessopp, UCC MaREI Centre, and expert angler, Jim Clohessy, Cork Harbour Angling Hub.
Jim Clohessy in Cork Harbour holds up a seabass
The authors have found that sea bass in Cork Harbour were highly resident, remaining within 1-3 kilomentres of where they were originally caught and tagged – a behaviour not known before this study. They also found that these localised fish returned to the same areas after their winter migration.
Sea bass is a large fish species only found in Irish and UK waters, and south into the Mediterranean and along North Africa. It is a commercially important species as it fetches a high price on the market. Sea bass is also an important fish for recreational anglers and is worth up to €70 to the Irish economy.
Despite very robust conservation measures in place in Ireland, sea bass populations in northern European waters have been declining since 2010, to the extent that the EU has introduced emergency measures to try to halt this decline.
These include catch restrictions on various bass fisheries; a large closed area around Ireland and Celtic Seas, and a one-a-day limit for recreational anglers. The International Council for the Exploration of the Seas (UNCLOS) has advised the EU Commission to impose a ‘no catch’ take in 2017, the study notes.
This study presents the first telemetry tracking movement of sea bass. Telemetry is the remote tracking of an animal using an electronic device (transmitter) and listening posts (acoustic receivers) and in this instance were strategically placed around Cork Harbour. The team used telemetry to track 30 individual fish for up to one year (2013-2015), swimming within 500 metres of a listening post.
“Knowing that sea bass return to the same little patch of coastal water each year is absolutely fascinating and asks so many questions about how they navigate and recognise when they are ‘home’. It also has important implications for conserving the species,” remarked Dr Doyle.
Fish left the harbour in October/November and returned the following May/June. Over 90% returned to Cork Harbour after their winter migration; 86% of which to the exact area they resided in before migrating, thus displaying high fidelity to local areas. Given their longevity (up to 35 years) and the combination of inter-annual fidelity to localised foraging areas, sea bass may be very suspectible to local depletion, the study notes.
“The marriage between science and angling in this study is fascinating,” remarked Jim Clohessy. “The results and some of the information has the potential to save the State a lot of money in terms of targeting their fisheries protection.”
Damien Haberlin added that very little was known about the movements of many familiar marine fish beyond some “very broad generalisations” that they are found inshore during the summer months and move offshore in the winter to reproduce.
“So in this context, our findings are very exciting.”
The research was funded by ESB and Science Foundation Ireland (under MaREI Centre), supported by the angling community (notably Richie Ryan and Andy Davies) in Cork Harbour.