The Fishery

Total landings for the coastal stock complex have declined from 470,000 mt in 1968 to 36,000 mt in 1983. (Table 22.1, Figure 22.2 [Fig 22.2 Data]). After the large offshore fishery collapsed in 1977, the fishery focused on near shore waters of the Gulf of Maine. Landings gradually increased from the mid 1980s through the 1990s and peaked at 133,000 mt in 2001. Landings declined slightly during 2002-2005, averaging 109,000 mt. The USA has accounted for about 72% of landings since 1978, but during the last decade has accounted for 85% of the total herring.

The fishery in the Gulf of Maine consists of fixed and mobile gear fisheries in coastal waters. Landings from the New Brunswick weir fishery ranged from 9,000 to over 44,000 mt during 1980-1998, while the mobile gear (purse seine and mid-water trawl) fisheries landed between 27,000-81,000 mt during the same period. There has been a great deal of annual variability in the landings, but little evidence of any long-term trend. However, changes have occurred in the distribution of landings between mobile and fixed gear fleets. Over the past five years, greater than 90 percent of Maine herring landings have been taken by U.S. mobile gear fisheries compared with less than 50 percent during the 1970s. This shift reflects reduced availability of herring to the fixed-gear fisheries and also less emphasis on this type of fishing. Current mobile gear landings are dominated by single and paired mid-water trawlers.

The Georges Bank herring fishery was initiated in 1961 by distant-water fleets. Landings peaked in 1968 at 373,600 mt and subsequently declined to 43,500 mt in 1976 as the fishery collapsed. Mid-water trawling by both USA and Canada herring fleets began in 1994, with landings peaking at 35,000 mt in 2001 and averaging about 13,000 mt during 1994-2005. The majority of Georges Bank herring landings are by USA mid-water vessels, with the balance taken by Canada.

Historically many age groups of herring (age 2-7) have been represented in the commercial landings (Figure 22.3 [Fig 22.3 Data]), as the inshore fisheries by the USA and Canada focused on younger fish while the offshore distant water fisheries targeted all age groups. After the offshore component had collapsed in the late 1970s and early 1980s, and the inshore component had been heavily fished, only age groups 2-3 were well represented in the landings. As the herring complex recovered in the late 1980s and the offshore fishery resumed, the age distribution of the landings expanded and ages 2-7 were prevalent. The recent fishery has been dominated by the strong 1994 and 1998 year classes, but many other recent cohorts have been moderate size or larger.

Biomass indices of herring in NEFSC spring and autumn research vessel surveys were relatively low during the 1960s and 1970s (Figure 22.4 [Fig 22.4 Data]). and declined even further in the late 1970s and early 1980s after the offshore component collapsed and the inshore component was greatly reduced. The survey indices markedly increased in the mid 1980s and early 1990s as recovery commenced, and have since remained relatively high although variable.

NMFS surveys have shown a progressively expanding age structure of herring in the Gulf of Maine-Georges Bank region since the early (Figure 22.5 [Fig 22.5 Data]).

Figure 22.2

Figure 22.3

Figure 22.4

Figure 22.5

Figure 22.6

Figure 22.7

Figure 22.8

Figure 22.9

Estimates of total stock biomass for the coastal stock complex exceeded 1 million mt before the collapse of the Georges Bank fishery. After the collapse in the early 1980s, stock size estimates declined to about 100,000 mt. Stock biomass has since increased substantiality primarily due to improved recruits. The offshore spawning component, which was the largest historic component of the stock complex, is now fully recovered.

Fishing mortality (2+) for herring declined from about 0.7 during 1970s to an average of 0.3 during the mid-late 1980s (Figure 22.6 [Fig 22.6 Data]). Thereafter, fishing mortality declined 0.1 in 1998 and has since remained at this level. Total biomass (2+) increased from about 105,000 mt in 1982 to about 1.3 million mt in 2000 but declined to 1.0 million mt in 2005 (Figure 22.7 [Fig 22.7 Data]). The increase in biomass the late 1990’s was primarily due to generally improved recruitment and two extremely large year classes, the 1994 and 1998 cohorts (Figure 22.7 [Fig 22.7 Data]). The 1994 year-class was the largest at about 7.2 billion, followed by the 1998 year class at about 5.5 billion and the 2002 year class at about 4.8 billion. Recruitment from the 1999-2000 and 2003 year classes is weaker than average.

Biological Reference Points

Yield per recruit reference points were estimated as: F_0.1= 0.21 and F_40%= 0.20 (Table 22.2).

The relationship between spawning biomass (SSB) and recruitment for the Gulf of Maine-Georges Bank herring complex during 1967-2003 and the geometric mean recruitment (horizontal line) are shown in (Figure 22.8 [Fig 22.8 Data]). Near average or better than average recruitment appear to occur at SSBs greater than about 700,000 mt. Recruit per spawner ratios were relatively high during the 1980s. Recent ratios have been greater than 1.0 (Figure 22.9 [Fig 22.9 Data]).

MSY reference points for the herring complex were re-estimated during the most recent (2006) assessment (Table 22.2). Results from a Fox surplus production model were F_msy = 0.31, MSY = 194,000 mt, and B_msy = 629,000 mt.

Summary

The Gulf of Maine-Georges Bank herring complex began to recover during the late 1980s and current total biomass (age 2+) is now comparable to the 1960s. Biomass increased from a low of about 105,000 mt in 1982 to near 1.3 million mt in 2001, and declined slightly to about 1.0 million mt in 2005, but is still substantially above the B_MSY (629,000 mt). Fishing mortality has remained low since the early 1990s and has averaged 0.1 since 2002 far below F_MSY (0.31). The stock complex is not overfished and overfishing is not occurring.