Striped bass (Morone saxatilis) COSEWIC assessment and status report: chapter 7

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Population Sizes and Trends

For the purposes of this section, the five known spawning populations are discussed separately.

Mark-recapture experiments to estimate population abundance have been conducted on only two of the five populations, those of the Miramichi and Shubenacadie rivers, and in only the last ten years. For populations or periods not covered by the estimates, only indirect abundance indices are available, e.g., records of commercial or recreational catches, sporadic surveys or experimental fisheries.

There are a number of reservations about the use of recreational or commercial catches to describe abundance trends in harvested fish species. The reservations are due, among other things, to the following factors: the data are not always collected and compiled in a consistent manner; the measurement of fishing effort is often lacking; and only the exploited segment of the populations is taken into account. Despite the constraints limiting the scope of their interpretation, catch statistics are often the only indices available for describing major trends in certain populations.

Southern Gulf of St. Lawrence (Miramichi River)

A compilation of commercial striped bass landings in the southern Gulf shows that the historical maximum (61 t) was reported in 1917 (LeBlanc and Chaput 1991) and was followed by a significant decline until 1934. No commercial landings were reported in the subsequent 33 years (from 1935 to 1968). This is attributed to the very low abundance of striped bass during that period (Douglas et al. 2003). Commercial catches resumed in 1969, peaking in 1981 at 48 t, then falling to less than 1 t in the early 1990s. The commercial striped bass fishery in the southern Gulf was closed in 1996.

Estimates of commercial landings between 1969 and 1996 were made on the basis of fish slips and fishery officer reports, two sources that are known to be incomplete and imperfect (Douglas et al. 2003). Research conducted by the Department of Fisheries and Oceans on the Miramichi River has shown that commercial striped bass catches were actually higher at this location than the amounts reported in the fishery statistics (Douglas et al. 2003).

Striped bass are taken predominantly as a bycatch in the gaspereau fishery and as a target species in the winter fishery (Douglas et al. 2003). Harvests are concentrated primarily along the coasts of Kent County, south of Miramichi (Kouchibouguac, Richibucto and Bouctouche areas). Commercial catches have also been reported in other New Brunswick counties, in the waters of Nova Scotia bordering the Gulf and in Prince Edward Island, but in much smaller quantities than in the Miramichi Bay area (LeBlanc and Chaput 1991).

Spawner estimates obtained in the Miramichi River since 1993 (Bradford et al. 1995; Bradford et al. 2001; Douglas et al. 2001) vary considerably (Figure 3). They show that spawner abundance fell from 50,000 in 1995 to approximately 8,000 in 1996 and 1997, and then to less than 4,000 between 1998 and 2000. It then increased to 24,000 in 2001 and to 29,000 in 2002 (Douglas et al. 2003). The sharp decline in spawner abundance in 1996 is believed to be due to the commercial fishery, which was subsequently closed. The recent recovery is believed to be due to the high survival rates of the 1998 year class.

Figure 3. Spawner estimates of northwest MiramichiRiverstriped bass since 1993 based on mark-recapture studies (Douglas et al. 2003).

Bay of Fundy tributaries

In summer, striped bass populations that spawn in Bay of Fundy tributaries can mix with migratory bass originating in U.S. rivers. As a result, certain precautions are required when estimating the size of these populations or determining the areas they frequent. 

Shubenacadie River

Only indirect abundance indices are available for Shubenacadie River striped bass for years prior to 1999. Sport fishery data suggest that a decline in striped bass abundance occurred in the Shubenacadie River between 1950 and 1975, but that the numbers subsequently remained relatively stable (Jessop 1991).

Immature and adult bass from this population ascend the Shubenacadie River, a tributary of Minas Basin, to overwinter in Shubenacadie and Grand lakes. In the spring, they return downriver. Spawners spawn in the Stewiacke River, a tributary of the Shubenacadie.

Mark-recapture experiments developed since 1999 to estimate the abundance of this population have targeted its downstream run, not only to prevent it from being confused with U.S. bass, which would distort the estimates, but also for practical reasons, i.e., it is easier to capture bass in the river than in the estuary.

Due to methodological and logistical problems in the first three years of the mark-recapture experiments (1999 to 2001), 2002 is the first year for which reliable abundance estimates are available. In 2002, the Shubenacadie River population totalled between 18,000 and 27,000, at least 15,000 of which were of minimum reproductive age (3 years or more) and at least 7,000 of which were 4 years and over.

Like the beach seine surveys of young-of-the-year, recaptures of tagged bass seem to suggest a summer range of this population in the inner portion of Minas Basin (Douglas et al. 2003).

This population is the only population of the Bay of Fundy group for which it has been possible to conduct sampling of young-of-the-year in recent years (Rulifson et al. 1987; Douglas et al. 2003). It is showing no evidence of decline. However, a sufficiently long time series of population estimates is not yet available to formally confirm that its abundance is stable.

Annapolis River

Surveys of recreational striped bass fishers in the Annapolis River suggest that this population declined from 1971 to 1978 (Jessop and Doubleday 1976; Dadswell et al. 1984). The data collected show not only significant variations in the number of catches but, more importantly, changes in the characteristics of the fish caught, indicating very low recruitment and an aging of this population since 1971: an increase in average length, weight and age, combined with a sharp decline in the proportion of young fish (Jessop and Vithayasai 1979; Williams et al. 1984; Parker and Doe 1981; Jessop 1980, 1990, 1991, 1995). Starting in 1975, the majority of bass captured were adults, with juveniles being rare (Dadswell et al. 1984; Jessop and Vithayasai 1979; Jessop 1980; Parker and Doe 1981). There is no evidence that new individuals have been produced since 1976.

Eggs seem to have been released in the river periodically, but very few appear to have survived. In 1994, 400 eggs were found, but no juveniles were captured during the summer and fall (Jessop 1995). There appears to be high mortality during the earliest developmental stages (eggs and larvae). No young-of-the-year were captured in beach seine surveys in the Annapolis River Estuary in 2001 or 2002 (Douglas et al. 2003).

Given the species’ longevity, it is possible, in principle, that bass from this population are still alive. However, it is believed that they can no longer reproduce due to water quality problems or to changes in water mass circulation, which are reported to cause egg mortality (see the section “Limiting Factors and Threats”).

Saint John River

There had been a striped bass fishery in the Saint John River estuary since the early days of colonization. Striped bass spawning was reported in the Saint John River, between Fredericton and Mactaquac, as far back as the late 1800s (Cox 1893).

Sport fishing for striped bass in the Saint John River was carried out primarily in summer in the Reversing Falls area, the rocky limit of the estuary. Bass taken at this location appear to be primarily fish of U.S.origin. Sport catches appeared to show significant annual fluctuations, coinciding with the indices of abundance of migrating populations from the U.S.(Dadswell et al. 1984; Douglas et al. 2003).

In contrast, the commercial fishery, which was primarily a winter fishery, targeted primarily the resident bass population (Dadswell 1976). At the outset, bass was a bycatch of Atlantic sturgeon fisheries (Acipenser oxyrhynchus).  Striped bass catches varied depending on the fishing effort directed at sturgeon. A winter striped bass fishery began in Belleisle Bay in 1930 (Dadswell et al.1984).

Landing statistics, collected since 1875, show significant fluctuations, with peaks generally being separated by 9- to 11-year intervals (Dadswell et al.1984). In the 1970s, commercial catches declined rapidly. An analysis of catch composition showed the absence of recruitment and confirmed that the population was in decline (Dadswell 1983). The commercial fishery in Belleisle Bay was closed in 1978 (Hooper 1991).

The last collection of eggs and of one young individual (1+) in this river dates back to 1979 (M.J. Dadswell, DFO memorandum, 2 February 1982, cited by Douglas et al. 2003). Systematic surveys conducted in 1992 and 1994 to collect eggs in June and juveniles in August were unsuccessful (Jessop 1995). Beach seine surveys in 2000 and 2001 were also unsuccessful (Douglas et al. 2003). Given the prolonged absence of evidence of spawning in this river, it must be concluded that this population has disappeared.

St. Lawrence Estuary

There is evidence that striped bass was fished by residents along the St. Lawrence Estuary under the French regime. Striped bass bones have been found, for example, on the site of an inn in Quebec City (Trépanier and Robitaille 1995).

The distribution, seasonal movements and harvesting of bass in the St. Lawrence Estuary were described in detailed at the end of the 19th century (Montpetit 1897). However, biological data on this species was systematically collected between 1944 and 1962 by the team of Dr. V.D. Vladykov, as part of a program to study and tag commercially harvested fish species (Brousseau 1955; Vladykov and Brousseau 1957; Beaulieu 1962; Magnin and Beaulieu 1967; Robitaille 2001).

The St. Lawrence striped bass population was very heavily exploited. The sport fishery was particularly intense around Île d’Orléans and in the Montmagny archipelago during the summer holiday period in July and August.

Striped bass was also caught by commercial fishers using fixed gear set along the shoreline, and by seiners, who used to catch striped bass off several islands in the St. Lawrence, between Île Madame and Île aux Oies. Commercial striped bass catches, which have been reported since 1920, show large fluctuations (from 5 to 50 t), with peaks being separated by approximately 10 years.

Judging from reported commercial landings, the St. Lawrence population appears to have declined significantly since the mid-1950s. In 1957, annual landings, which had always fluctuated between 5 and 50 tonnes, dropped below 3 tonnes, where they remained until 1965, the last year for which commercial catches of this species were reported.

Recreational landings seem to have followed the same trend. The last landings of striped bass in the Montmagny fishing tournament were in 1963. Occasional catches were landed by sport fishers until 1968 (Robitaille and Girard 2002).

It was briefly believed that this population had recovered in about the early 1980s, when some 100 bass were caught in Quebec, primarily around the Gaspé Peninsula and in the lower estuary. However, various indices, including tags found on a number of individuals, suggested that they were actually bass from the Miramichi River (R. Bradford, pers. comm.).

When bass was present, it was common to catch hundreds of young-of-the-year in fixed gear set around Île d’Orléans. This has not been the case since the mid-1960s. No other evidence of spawning has been observed since then.

Only one abundance estimate is available for this population. In the fall of 1957, between 600 and 1,300 two-year-old bass were surveyed in a coastal segment of approximately 60 kilometres, along the south shore (Robitaille 2001). This estimate is of limited interest because it was made after the striped bass population had already declined significantly. In addition, it applies essentially to the 2-year-old age group and cannot be extrapolated to other years or to the entire population.