Striped red mullet in the North East Atlantic, Gillnet
In the Northeast Atlantic, striped red mullet is mainly taken as bycatch in demersal trawl fisheries targeting commercially more important roundfish species such as Atlantic cod (Gadus morhua) and haddock (Melanogrammus aeglefinus). Landings are mainly taken from Subarea VII and VIII, and especially by France. Striped red mullet is a target species for French bottom trawlers operating in the Eastern English Channel and south of the North Sea. In the Western English Channel, striped red mullet is also caught in lesser magnitudes by set gillnets. The north of the Bay of Biscay (VIIIa,b) is exploited by France and Spain. The south (VIIIc) is only exploited by Spain (ICES, 2014).
Annual landings of striped red mullet have increased from a low of 202 tonnes in 1978 to a high of 1009 tonnes in 1991 (Figure 1). On average, landings were 975 tonnes per year in the Northeast Atlantic between 1977 and 2013. Population abundance has fluctuated throughout the time-series with a decreasing trend in the last few years (ICES, 2014).
No information on recruitment, spawning stock biomass or fishing mortality is available for this data-limited stock.
Stock structure and recruitment
Limited information on the structure of the striped red mullet stock in the Northeast Atlantic is available. A study comparing the geometrical morphometry of striped red mullet in Northwest European Seas identified morphological differences in red mullets inhabiting the Eastern English Channel and the Bay of Biscay (Benzinou et al., 2013). Results from this study suggest that the striped red mullet can be geographically divided into three zones: (1) the Bay of Biscay; (2) a mixing zone composed of the Celtic Sea and the Western English Channel; and a northern zone composed of the Eastern English Channel and the North Sea (3).
Data gaps and research priorities
Although striped red mullet is economically-important, there has been a lack of data collection and research on the population dynamics of this species. As such, ICES classifies this stock as data-limited and there is little information available to evaluate the status of the stock (ICES, 2014).
At present, there is an informal stock assessment based on temporal trends in commercial catch rates including age and length sampling from the Celtic Sea and the Bay of Biscay that began in 2008. Since the introduction of the concurrent sampling design in 2009, more data, such as length compositions, have been made available for investigation. Abundance estimates for striped red mullet in the Northeast Atlantic are provided by one standardised research survey conducted annually in the Celtic Sea and the Bay of Biscay since 1997. Additional research surveys should be carried out along the Spanish coasts between the Portuguese coasts and the Bay of Biscay to provide more information on stock structure and recruitment (ICES, 2014).
Further studies focusing on the population dynamics and exploitation characteristics are required to provide a better understanding of stock status. Existing biological information is sparse and many of the basic life history parameters for this data-limited stock remain unknown.
Benzinou A, Carbini S, Nasreddine K, Elleboode R, Mahé K. 2013. Discriminating stocks of striped red mullet (Mullus surmuletus) in the Northwest European seas using three auto-matic shape classification methods. Fisheries Research 143 (2013) 153–160.
ICES. 2014. Report of the Working Group on Assessment of New MoU Species (WGNEW), 24–28 March 2014, Copenhagen, Denmark. ICES CM 2014/ACOM:21. 162 pp.