Single-stock exploitation boundaries


Exploitation boundaries in relation to precautionary considerations


There are indications that the biomass and recruitment has increased in the recent years. There are no indications that the current catch level is detrimental to the stock and therefore the advice for 2008 is not to increase the catches above the most recent catch of 9400 t (2006).

Management considerations


Plaice is taken both in a directed fishery and in a mixed cod-Nephrops-plaice fishery. The stock area for North Sea cod includes the Skagerrak (Division IIIaN). Both North Sea cod and Kattegat (Division IIIa South) cod are well below B_lim. Thus, monitoring of the mixed fishery in terms of cod bycatch and discarding should be continued, and measures to prevent significant cod bycatch should be considered.
A summary of biological inference on stock entity on plaice in these waters can be summarized as follows: Plaice in Eastern Skagerrak and Kattegat mix and Western Skagerrak plaice might be recruited partly from the North Sea. Kattegat plaice may expand its distribution area to the Belt Sea, but there is evidence of insignificant connection with the Western Baltic plaice stock. In conclusion, the current management area of Division IIIa appears appropriate with regards to the biological identity of the stock. However, most catches are reported at the boundary with the North Sea stock distribution, where their exact stock origin is uncertain. This may affect the appropriateness of the management because the basis for the advice is based on the catch levels and not on the assessment based on survey indices.

The IBTS survey as well as the application of the data should be intensified in Division IIIa.

Ecosystem considerations


The large-scale circulation pattern in the northern Kattegat depends mainly on the interaction between Baltic runoffs and local variations due to wind stress. Nielsen et al. (1998) demonstrated that the abundance of settled 0-group plaice along the Danish coast of the Kattegat depends on transport from the Skagerrak. The 0-group abundance measured in July–August was significantly higher in years when wind conditions during the larval development period (March–April) were moderate to strong. This might imply that larval plaice are food-limited in years when calm conditions prevail during the larval drift period (Nielsen et al., 1998). There are consistent migration patterns of adult fish in the northwestern direction, from South Kattegat to North Kattegat and from North Kattegat to Eastern Skagerrak.

There are no explicit management objectives for this stock.

Catch andd TACs
Catch and TACs
Weights in ‘000 t.
¹⁾ In March 2002 ACFM revised its advice to 11.6 for both areas combined.
²⁾ The TAC for the two areas combined was adjusted to 11 200 tonnes in mid-2002.
³⁾Single-stock boundary and the exploitation of this stock should be conducted in the context of mixed fisheries.