Information identified as archived on the Web is for reference, research or recordkeeping purposes. It has not been altered or updated after the date of archiving. Web pages that are archived on the Web are not subject to the Government of Canada Web Standards, as per the Policy on Communications and Federal Identity.
Legal Listing Consultation Workbook for the Atlantic populations of Blue Shark, Shortfin Mako and White Shark
Of all the non bottom dwelling (pelagic) sharks in the world, blue sharks Prionace glauca are the most abundant and widely distributed. They are easily identified by their distinctive coloration which is dark blue on top changing to bright blue on the sides and white on the belly and can reach over 3.8 m in length. They also have a characteristic notch at the top of their caudal fin and long sickle-shaped pectoral fins.
Blue sharks are a highly migratory species found around the world including both hemispheres of the Atlantic and Pacific Oceans. Tagging studies in the northwest Atlantic indicate that although blue sharks move across the equator, populations generally appear to be separated by hemisphere. These studies further indicate that blue sharks may migrate in a clockwise direction from west to east across the North Atlantic.
In Atlantic Canadian waters, blue sharks appear to be migrating through our waters in late summer to early fall. Catches have been recorded along the edge of the continental shelf from northeastern Newfoundland, to the Gulf of St. Lawrence, and Bay of Fundy.
Blue sharks are typically found in the upper layer of offshore waters from the surface to 350 m. Their preference for water temperatures between 10 and 200 C is likely the determining factor for depth and area of distribution. It also appears that blue sharks are separated by size and sex in the northwest Atlantic, indicated by an absence of mature females off the northeastern United States and Canada.
Blue sharks are considered to be opportunistic feeders, eating a wide variety of prey species including fish, squid, birds and carcasses of marine mammals.
Mating for blue sharks appears to take place outside Canadian waters from spring to early summer with a gestation period of 9 to 12 months. With an average litter size considered to be 25 to 50 every two years, blue sharks are one of the most prolific shark species in the world. Newborn pups are generally between 35 and 60 cm in length. Males reach sexual maturity between 193 and 210 cm while females mature at lengths greater than 185 cm. Age of maturity for both sexes is between 4 and 6 years with a maximum lifespan of between 16 and 20 years. The annual population growth rate for blue shark has been estimated at approximately 43% which, along with the blue sharks large litter size, likely help to slow their population decline despite high catch mortalities.
COSEWIC provides the following rationale for designating blue shark as special concern (SC):
This species is a relatively productive shark (maximum age 16-20 years, mature at 4-6 years, generation time 8 years, 25-50 pups every two years) but as an elasmobranch, populations are susceptible to increased mortality from all sources including from human activities. The species is considered to have a single highly migratory population in the North Atlantic, of which a portion is present in Canadian waters seasonally. The abundance index which is considered to best represent the whole population has declined 60% 1986-2000 but another index shows no long-term trend for the whole population 1971-2003. Indices of abundance in and near the Canadian waters show variable trends from no decline to 60% decline from the 1980s to early 2000s. There is evidence for a decline in mean length in longline fisheries in Canadian waters 1986-2003. The primary threat is bycatch in pelagic longline fisheries; although the threat is understood and is reversible, it is not being effectively reduced through management. Assessing the impact of bycatch on the population would benefit from better information on proportion of individuals discarded which survive. It appears that recent fishery removals from the North Atlantic have been several tens of thousands of tons annually. Estimated Canadian removals, a small proportion of the total, have been declining since the early 1990s and recently have averaged around 600 t/yr.
Threats to Blue Shark
The COSEWIC status report identifies bycatch in pelagic longline fisheries as the primary threat to blue sharks. Since effort in these fisheries has increased 10 fold over the last 50 years in the North Atlantic, it is assumed that the bycatch of blue sharks has increased at the same rate. Unfortunately, because of the poor quality of meat, blue sharks are generally discarded at sea although it is estimated that as high as 60% survive being captured. In Canadian waters, however, it is estimated that blue shark catches represent only approximately 1% of their catches world wide. Current catch mortalities of blue sharks in Atlantic Canadian waters have declined from over 1500 t/yr in the early1990s to less than 1000 t/yr between 1996 and 2002. Finning (the practise of removing and keeping the fins to sell while discarding the carcasses) for blue shark is also considered a source of mortality particularly in international waters. Although the yearly take of blue shark fins is unknown, it is estimated that they make up more than 50% of that market.
Protecting Blue Shark
Blue Sharks are managed under the Canadian Atlantic Pelagic Shark Integrated Fisheries Management Plan. Although a directed fishery with a precautionary allocation of 250 t is allowed under this plan, there are no real markets for the meat due to rapid spoilage at sea. The plan also allows for an unrestricted bycatch of blue sharks in other large pelagic fisheries but requires 100% dockside monitoring of both the directed and bycatch fisheries. The recreational fishery for blue sharks in Atlantic Canada is “catch and release” only, unless caught during a fishing derby when carcasses may kept for scientific purposes. Finning has been prohibited in all Canadian waters since 1994.
Potential Impacts on Stakeholders
If added to the List of Wildlife Species at Risk, activities that affect the blue shark or its habitat may receive more scrutiny. While automatic prohibitions do not apply to species of special concern under SARA, a SARA Management Plan will be required and a range of management measures may be implemented to conserve the blue shark population.
These measures may lead to a variety of impacts on stakeholders, including additional costs. The following list is not exhaustive; please use this consultation workbook as an opportunity to list omissions.
Management strategies that could affect Aboriginal people fishing for food and social purposes and communal commercial fisheries purposes in areas inhabited by blue shark may be considered.
If a particular fishing activity is identified to be a concern for the survival and recovery of a listed species, management measures may be taken to address the concern. These measures could include increased observer coverage in certain areas, closed areas, gear modifications, or other activities developed in collaboration with industry that willhelp prevent and minimize interactions.
Restrictions and management measures may be imposed to limit recreational activities that may affect the survival and recovery of blue shark.
Those wishing to carry out research on blue shark or in areas of their habitat may be required to comply with stricter guidelines. This may limit the type and/or duration of research permitted on blue shark and may lengthen the preparation time required for planning research projects.
Maritime Forces Atlantic may be asked to prepare guidelines for naval exercises in areas frequented by blue shark. They may be asked to refrain from undertaking specific types of exercises in these areas. As identified in SARA, these requirements would be waived in emergencies or if national security were affected.
Shipping, oil and gas operations and other marine activities may be impacted by listing blue shark under SARA. However, no specific threats from these or other activities have been identified.
All proposed marine activities that fall under the Canadian Environmental Assessment Act (CEAA) will need to address the impacts on SARA listed species in accordance with this legislation.
COSEWIC 2006. COSEWIC assessment and status report on the blue shark (Atlantic population) Prionace glauca in Canada. Committee on the Status of Endangered Wildlife in Canada. Ottawa. vii + 46 pp.
DFO, 2002. Canadian Atlantic Pelagic Shark Management Plan 2002-2007.
- Date Modified: