Red mullet migration into the northern North Sea during late winter

The abundance of red mullet (Mullus surmuletus) caught by trawl net during research surveys around the coast of Scotland has soared since 1995. Almost none were recorded for a total of 70 years between 1925 and 1995. Then, starting in January1995, red mullet began to appear in numbers to the west and east of Scotland. The exception to the almost total absence for 7 decades is a small peak in numbers, centred on the late 1940s when 19 red mullet were recorded in the Fisheries Research Servicesʹ (FRS) demersal sampling area ‘Buchan’ from a total of 329 trawl hauls. Interestingly, all the red mullet caught by FRS since 1995 have been taken during the first quarter of the year despite active sampling in quarter 3. This observation is puzzling. In an attempt to explain it, the authors postulate that the red mullet entering the northern North Sea in quarter 1 are in reality part of an increasing southern North Sea population that migrates northwards where water temperatures are higher during wintertime.