Atlantic mackerel, Scomber scombrus,
is a fast swimming, pelagic, schooling species distributed in
the Northwest Atlantic between Labrador and North Carolina. There
are two major spawning components in the population: a southern
group that spawns primarily in the Mid-Atlantic Bight during April
and May, and a northern group that spawns in the Gulf of St. Lawrence
in June and July. Both groups winter between Sable Island (off
Nova Scotia) and Cape Hatteras in waters generally warmer than
7°C (45°F), with extensive northerly (spring) and southerly
(autumn) migrations to and from spawning and summering grounds (Figure
23.1). The two groups are managed as a unit stock. Maximum
observed size in recent years is about 42 cm (16.5 in) in length
and 1.0 kg (2.2 lb) in weight. Sexual maturity begins at age 2
and is usually complete by age 3. Maximum age is about 20 years.
Mackerel are subjected to seasonal fisheries, both commercial
and recreational, throughout most of their range. U.S. commercial
landings are taken primarily between January and May in southern
New England and Mid-Atlantic coastal waters, and between May and
December in the Gulf of Maine. U.S. recreational catches occur
mainly between April and October. Canadian commercial landings
have typically been taken off Nova Scotia, in the Gulf of St Lawrence,
and Newfoundland between May and November.
The U.S. fishery is managed using annual quotas under the Mid-Atlantic
Fishery Management Council's Atlantic Mackerel, Squid, and Butterfish
Fishery Management Plan. The information provided herein reflects
the results of the most recent peer-reviewed assessment for Atlantic
mackerel (NEFSC 2006).
Atlantic mackerel were heavily exploited
by distant water fleets during the late 1960s-early 1970's. Total
landings averaged 350,000 mt during 1970-1976 but decreased to less
than 50,000 mt during 1978-1984 (Table 23.,
23.2 Data]). Landings in Canadian waters remained relatively
stable at an average of 24,000 mt during 1968-2000, where landings
in US waters increased during 1985-1991 to an average of 76,000m
mt, with the advent of a joint venture fishery in the Mid-Atlantic
region. Recently both USA and Canadian landings have increased due
to improved demand. U.S. landings increased from 5,646 mt in 2000
to 53,724 mt in 2004; Canadian increased from 13,383 mt in 2000
to 51,444 mt in 2004, declining to 41,234 mt in 2005. USA recreational
landings averaged 1,344 mt during 1990-2000, declined to only 467
mt in 2004, and then increased again to 1,042 mt in 2005.
Many age groups were present in the
mackerel landings during the late 1960s and early 1970s, but the age structure
of the landings became very truncated after the stock collapsed in the
late 1970s. As the stock recovered in the late 1980s and early 1990s,
the age distribution expanded and age groups up to 10 were again represented
in the landings. Older fish have not been present in the landings during
the last several years, but this is mostly due to an availability problem
Several large cohorts were produced
in the stock during 1968-2005 (Figure
23.5 Data]). The 1967, 1982, and 1999 cohorts were relatively strong.
Moderate year-classes and expansion of the age structure are apparent
during the late 1980s through 1998. Large catches at age 1 and 2 for mackerel
have dominated the survey catches in recent years. Recent surveys also
show an apparent lack of older fish.
Fishing mortality (ages 4-6, unweighted) was high
during 1969-1975, peaking at 0.54 in 1975 (Figure
23.6 Data]), and then sharply declined to 0.05 in 1978 followed
by a very low and stable period during 1979-1986. Fishing mortality
increased very slightly in 1988 to 0.09, (coincident with the joint
venture (JV) fishery that operated for several years), and then declined
and has since been below 0.06. Spawning biomass peaked in 1972 at 1.7
million mt, declined until 1976, and has increased thereafter reaching
a record high of 2.3 million mt in 2003-2004 (Figure
23.7 Data]). Recruitment ranged between 0.1-5.8 billion fish during
1962-2004 and averaged 1.1 billion fish (Figure
23.8 Data]). Three large year-classes were produced during this
period, the 1967, 1982, and 1999 cohorts. The 2003 and 2004 cohorts
appear to be above average but their magnitude is still uncertain.
Biological Reference Points
Yield and spawning stock biomass reference points
are shown Table 23.2. These reference points were
re-estimated in the most recent (fall 2005) assessment as F0.1
= 0.25 and F40% = 0.24 (NEFSC, 2006).
The spring stock recruitment relationship for Atlantic
mackerel is highly variable with strong year classes produced at both
high and low spring stock levels. Survival ratios have been relatively
low during 1962-2005 with the exception of the four largest year-classes
23.9 Data]). Recent R/S ratios have been very low except for the
MSY reference points were estimated in the most recent
(Fall 2005) assessment and MSY = 89,000 mt, SSBmsy = 644,000
mt, and Fmsy = 0.16 (NEFSC, 2006).
Spawning stock biomass has increased steadily since
1978, reaching a recent high of 2.3 million mt in 2004, for BMSY
(644,000 mt). Fishing mortality has remained very low (below F=0.06)
since 1992. Therefore, the stock is not overfished and overfishing is
Anderson, E. D., and A .J. Paciorkowski.
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L. Hudon, and J. Lavers. 2003. Atlantic mackerel (Scomber
scombrus L.) fishery and biology in NAFO Subarea 3 and 4
in 2002. DFO Canada Sci. Advis. Sec. Res. Doc. 2003/085. 36 p.
Grégoire, F. 2005. Update (September
2005) of the Atlantic mackerel (Scomber scombrus L.) landings
in NAFO Subareas 3 and 4 in 2004. DFO Can. Sci. Advis. Sec. Res. Doc.
Overholtz, W. J., S. A. Murawski,
W. L. Michaels, and L. M. Dery. 1988. The effects of density dependent
population mechanisms on assessment advice for the northwest Atlantic
mackerel stock. NOAA Tech. Memo. NMFS-F/NEC-62.
Overholtz, W. J., S. A. Murawski,
and W. L. Michaels. 1990. Impact of compensatory responses on assessment
advice for the Northwest Atlantic mackerel stock. Fish. Bull., U.S.