Every year in late spring, thousands of mysterious underwater craters start appearing in gravelly and sandy seabeds along the south coast of England. The culprit: Black Sea Bream. Males of this small fish excavate a nest by vigorously beating their tails to clear sand and gravel, and using their mouths to drag larger items, until they expose an area of clean, flat rock. This is the perfect place for a female to lay eggs, which the male guards diligently for several weeks until the larvae emerge.
In Sussex, Black Sea Bream nests are so densely packed that huge areas of seabed can resemble the surface of the moon– a true feat of ecosystem engineering. However, this fascinating aggregation behaviour can make the Black Sea Bream vulnerable to human disturbance. Black Sea Bream are economically important as targets for recreational angling and commercial fishers, but some fishing activities such as trawling can be disastrous for nesting Sea Bream, as it can destroy nesting areas. Recently, efforts to protect Sea Bream have included limiting fishing activities in known nesting areas such as the Kingmere Marine Conservation Zone and the Sussex IFCA Nearshore Trawling Byelaw, with anecdotal evidence suggesting an increase in Black Sea Bream nesting activity and populations in some areas.
Recently, researchers from the University of Plymouth in collaboration with Natural England, Sussex IFCA and Sussex Wildlife Trust have been using electronic tagging and tracking to understand Black Sea Bream movements during and outside their nesting season, and the results have been fascinating. Black Sea Bream caught on nesting areas in Sussex, undertook seasonal migrations spanning hundreds of miles, moving as far afield as western Brittany and Cornwall during the autumn and winter. The researchers also found that tagged individuals show an impressive homing ability, returning to within a few metres of previously used nesting sites, over multiple consecutive years. Movement information such as this is difficult to obtain, but is vital for ecosystem-based management of fish populations, telling us where and when protection might be applied.
You can find out more about this research and its applications here, and the wider animal tracking work conducted by the Plymouth team as part of the Fish Intel Network.
Written by guest author Dr Pete Davies, Applied Marine Ecosystem Research Group, University of Plymouth. Contact: [email protected]
