Due to widespread exploitation of this species, accurate assessments of abundance are hard to produce (Forgarty 1995). This said, it is believed this species’ population has been “relatively robust under exploitation” (Forgarty 1995:132). Causes for this resilience are unknown, although Anthony and Caddy (1980) suggest the “role of refugia of lightly exploited groups that provide a larval subsidy to more heavily exploited groups.” (Fogarty 1995:132).
A more detailed picture of the population dynamics can be ascertained by sectioning the population by fisheries. In the
The commercial landings of this species have generally shown an upward trend since 1981; from around 15,000 mt to a peak of 36,500 mt in 2004 (Idoine 2006). Abundance indices indicate a large degree of inter-annual variation in both male and female abundance; however there is a general upward trend until 2005 when there is a sharp decline from around 2.0- 2.5 down to 0.5-1.0 (stratified mean number per tow, Idoine 2006). However, the 2006 data shows an increase again to between 1.0-1.5 stratified mean number per tow (Idoine 2006).
Abundance estimates are currently well above the target of 69.62 million lobsters (Idoine 2006). In 2003, the abundance was estimated at around 100 million individuals (Idoine 2006).
Between 1982 and 2000, landings in this fishery were relatively stable and fluctuated between 1,000 mt and 1,700 mt. In 2000 they then increased up to a peak of 2,300 mt in 2005.
Abundance indices for males and females have shown similar trends since 1981 with female index increasing from around 0.72 to 1.51 stratified mean number per tow in 2002, and the male index increasing from around 0.62 to 0.98 stratified mean number per tow (Idoine 2006). However, both indices have since declined to around 1.04 and 0.23 (stratified mean number per tow) for females and males respectively in 2006. Abundance of lobsters has also shown considerable fluctuations since 1982 between 6 million and 9.5 million lobsters (Target = 8.61 million, threshold = 7.95 million, Idoine 2006). Since 2001 abundance has been above the target at about 9 million lobsters (Idoine 2006).
Landings from this fishery started at around 2,500 mt in 1982, and peaked at 10,100 mt in 1997. They have since declined to around their 3,000 mt in 2005, which is around the 1982 level.
Survey indices conducted by Connecticut show a greater number of males than females in the tows, with both peaking at 25 and 12 respectively in 1997. Subsequently there has since been a decline to 1.31 for females and 2.88 for males (stratified mean number per tow, Idoine 2006).
Abundance estimates for this species were low in the 1980s and below the threshold of 22.31 million lobsters, but peaked at 45 million lobsters in 1997 (above the target of 23.9 million lobsters, Idoine 2006). They have subsequently declined again to a record low of 12.3 million in 2003 and are currently estimated at around 14 million (Idoine 2006).
Gulf of St. Lawrence - LFAs 23, 24, 25, 26a, 26b
Landings in this fishery were at around 8,000 tonnes in the 1950s and peaked in the 1990s at around 18,731 tonnes. There has since been a decline in the landings to ~17,012 tonnes in 2001. Landings per unit area (LPUA) are considered an index of productivity within a given fishing area. From the 1970s through to the 1990s all fishing areas showed an increase in LPUA. There was a decline in landings in 2000; apart from LFA 24, which showed a further increase. Information on fishing effort from each of the separate fishing grounds indicates that fishing effort in all regions has remained relatively constant between 1984 and 2001. Exploitation rates are high in all fishing areas at around 70% (Fisheries and Oceans Canada 2002).
Lobster landings is Quebec have shown an upward trend since the 1970s and rose to 3,135 tonnes in 2003. Sixty six percent of these landings came from: Magdalen Island (28.5%), Gaspé Peninsula (3.6%), Anticosti Island, and the North Shore (1.3%). Exploitation rates are high at: 75% in the Magdalen Islands, 85% in the Gaspé Peninsula, and 20% at Anticosti Island.
Catch per Unit Effort (CPUE) data for the Magdalen Islands indicates a peak in 1992 at around 1.1 numbers/trap or 0.55 kg/trap with a subsequent decline. However, CPUE has remained relatively stable since 1994/1995. This trend is said to generally reflect the trend in the southern archipelago.
CPUE data for this region shows an increase from around 0.5 numbers/trap in 1988 to ~0.85 numbers/trap in 1996. There has since been a decline to around 0.45 numbers per trap in 2004 which is below the average for 1986-2002.
CPUE ranged between 0.2 and 0.4 numbers/ trap between 1993 and 2003; with the lowest value being recorded in 2002. In 2003 it rose again, but is still below the average.
Eastern Cape Breton - LFAs 27-30
Landings of this species have fluctuated greatly over time. They peaked at around 4000 tonnes in 1990 and subsequently declined to between 1,480 tonnes in the late 1990?s. They have since shown an increase in 2001 to 1,987 tonnes. Mean catch rates (expressed as kg per trap haul) have generally remained stable in all fishing areas other than a noted decline in LFA 27 and LFA 30 in 1997, however these have since stabilized (Fisheries and Oceans Canada 2004a).
Eastern Shore Fishery - LFAs 31A, 31B, 32
Landings data shows an upward trend in all areas between 1993 and 2000 with a very slight decline in 2001. The catch rate (expressed as kg/trap haul) has also shown an increase in all areas between 1996 and 2002. There was no overall increase in the median size of individuals in each area and no overall increase in the number of observed berried females despite put-backs (Fisheries and Oceans Canada 2004b).
Nova Scotia - LFA 33
Since 1989 the landings of this species have increased to around 2,753 mt in 2001/2002. Indicators of pre recruit numbers/trap haul showed no overall change or a negative trend between 2000 and 2003. The number of observed berried females however, has increased from 2000. Exploitation levels also declined during the period 1999-2003 (Fisheries and Oceans Canada 2004c).