Research Document - 2003/058
Lobster stock status in the Magdalen Islands (LFA 22) in 2002
By Gendron, L., and Savard, G.
Abstract
Lobster landings in the Magdalen Islands reached 2,024 t in 2002, compared with 2,177 t in 2001, representing a 7% decrease. Landings were 4 % below the average of the years 1985-2001 (2,110 t), which include years where historic high levels of landings were recorded. In a longer term perspective, landings in 2002 were 12% higher than the 25-year average (1977-2001) of 1,812 t.
The 2002 fishing season was slightly colder than the preceding years, which may have had an effect on catchability. In 2002, the average CPUEs in number of lobster for the entire Magdalen Islands were 13 % below the series average (1985-2001), but in terms of weight of lobster, they were 2 % above the average. CPUEs in number were lower in 2002 compared to 2001 both in southern and northern Magdalen Islands. However, decreases of CPUEs in weight were a little less.
The mean size of lobsters caught increased by approximately 5 mm in 2002 compared to 1996. In 2002, the proportion of “market” lobsters (≥ 83 mm) was >90%, compared with averages of 54% (south) and 65% (north) in 1996. The proportion of jumbo lobster (≥ 127 mm CL) remains very low (< 1%). Exploitation rates for commercial-size male lobsters remain high in the southern and northern Magdalen Islands and are above 70 %. Exploitation rate of the fraction of the population ≥76 mm has decreased to approximately 45 % since the minimum catch size was increased.
The results of a simulation model show that with the 6-mm increase in minimum catch size, egg production per recruit appears to have increased by approximately 75% from 1996 levels. The objective of doubling egg production per recruit should be reached by increasing minimum catch size to 83 mm. The abundance of berried females has increased in the population but egg production probably mainly comes from first spawners (primiparous).
The abundance indices of recruitment to the fishery suggest that current landing levels could be maintained in 2003. However, prerecruit and juvenile abundance indices were down during the trawl survey in 2002, suggesting a possible drop in fishing recruitment in the coming years.
The conservation measures taken since 1997 have had a tangible, positive impact on lobster stocks. Egg production has increased and the growth potential of lobster is better expressed. Doubling egg production per recruit is the first step in meeting the conservation objectives that are also intended to ensure the distribution of egg production between first spawners and mulltiple spawners and to widen the size structure of stocks. Exploitation rates remain high and need to be reduced. Such high exploitation rates make the fishery heavily dependent on annual recruitment, offset the expected benefits of increasing the minimum catch size, and slow down the increase in the proportion of multiparous females in stocks.
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