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Legal Listing Consultation Workbook for the Atlantic populations of Blue Shark, Shortfin Mako and White Shark
The shortfin mako (Isurus oxyrinchus) is one of five species in the family commonly known as mackerel sharks which includes the great white shark and basking shark. The mako shark is described as spindle shaped, deep blue to purple above and white below, with a conical head, sharply pointed snout and crescent shaped caudal fin. The u-shaped mouth has large sharp teeth that protrude outside of the mouth even when closed. It can reach a maximum length of over 4 m. There are no scientific surveys for shortfin mako conducted in Canadian waters.
Shortfin mako are found around the world from temperate to tropical waters. In the northwest Atlantic they have been found both inshore and offshore, from Bermuda to the Gulf of Maine. In Canadian waters where they are considered at the edge of their range, they have been recorded from the Grand Banks off Newfoundland, along the Scotian Shelf and down to Georges Bank.
Tagging studies indicate that shortfin makos are highly migratory with distribution apparently dependent on water temperatures which they prefer between 17 and 22o C. They migrate to the Atlantic coast of Canada generally in the late summer and fall where they are usually associated with the warm waters of the Gulf Stream. They are extremely adaptable and able to withstand significant changes in temperature as well as changes in food availability over its wide range. Shortfin mako feed primarily on other fishes including tuna, mackerel, bluefish and swordfish, but may also eat marine mammals.
Unlike most other sharks, mackerel sharks are able to regulate their body temperatures which the shortfin mako, in particular, maintains at 1 to 10o C above its surrounding water temperature. This allows the shortfin mako (one of the fastest sharks in the world) to sustain its high swimming speeds when migrating through colder, deeper waters.
Females mature at lengths of 2.7 to 3 m and give birth to a litter size of 4 to 25 pups after a gestation period of approximately 15 to 18 months. Pups are approximately 70 cm at birth. Although males mature slightly smaller at 2 to 2.2 m, minimum age of maturity for both sexes is 7 to 8 years. The minimum lifespan has been estimated at 24 years with a maximum life expectancy of up to 45 years.
COSEWIC provides the following rationale for designating shortfin mako as threatened(TH):
As a large (maximum length 4.2 m), relatively late-maturing (7-8 yrs) pelagic shark, the species has life-history characteristics making it particularly susceptible to mortality from all sources, including human activities. The species is circumglobal in temperate and tropical waters. Individuals found in Canada are considered part of a larger North Atlantic population. There does not appear to be any reason to assume that the Canadian Atlantic "population" is demographically or genetically independent from the larger Atlantic population, so the status of the species in Atlantic Canada should reflect the status throughout the North Atlantic. Although there is no decline in an indicator of status for the portion of the species that is in Atlantic Canada, two analyses suggest recent declines in the North Atlantic as a whole (40% 1986-2001; 50% 1971-2003). The main causes of the species' decline (mortality due to bycatch in longline and other fisheries) are understood and potentially reversible, but these sources of mortality have not been adequately reduced.
Threats to Shortfin Mako
COSEWIC has identified fishing and pelagic longlining in particular, as being the most significant threat to the shortfin mako. There are no reliable abundance estimates for this species and the largely unmonitored longlining effort in international waters increases the uncertainty in abundance trends. Studies of bycatch in Atlantic Canadian waters indicate that shortfin mako make up 2 to 3% of the total weight of the pelagic longline fishery for swordfish. Because the meat is highly prized, this bycatch is rarely discarded at sea.
International studies based on American and Japanese longline data indicate catch rate declines of 40 to 50 % for shortfin mako. While these declines have not been observed in Atlantic Canadian waters, preliminary studies do indicate a recent decline in the abundance of larger individuals.
Shortfin makos are also sought after by sport fishers who value them for their “fighting” ability as well as their edible flesh.
Protecting Shortfin Mako
There is no directed fishery for shortfin mako in Atlantic Canada, but it is caught as bycatch in other pelagic fisheries including swordfish, shark and tuna. Shortfin makos are managed under the Canadian Atlantic Pelagic Shark Integrated Fisheries Management Plan which allows for an unrestricted bycatch along with 100% dockside monitoring. The recreational shark fishery is “catch and release” only except in the case of a fishing derby when carcasses may be kept for scientific purposes. Also, the practise of “finning”, (removing and keeping the fins to sell while discarding the carcasses) has been prohibited in all Canadian waters since 1994.
Potential Impacts on Stakeholders
If added to the List of Wildlife Species at Risk, shortfin mako will be protected under SARA. If particular activities are assessed to be a threat to the survival and recovery of a listed species, management measures will be put in place to restrict those activities and ensure the protection of species at risk.
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 any omissions.
Management strategies that could affect Aboriginal people fishing for food and social purposes and communal commercial fisheries purposes in areas inhabited by shortfin mako sharks may be considered.
It is important to fully determine the extent of potential threats to shortfin mako by any fishing activities. Once these species are listed, prohibitions will apply to fishing activities identified to be a threat to their survival and recovery. Some level of bycatch may be allowed for fishing activities that take shortfin mako incidentally, but only if measures are taken to minimize the impact of the activity on these species and the bycatch level will not impede their recovery. Current SARA legislation however, does not permit this bycatch to be retained.
Maritime Forces Atlantic may be asked to prepare guidelines for naval exercises in areas frequented by shortfin mako. 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.
Restrictions and management measures will be imposed to limit recreational activities that may affect the survival and recovery of shortfin mako. The recreational fishery for shortfin mako would not likely continue.
Those wishing to carry out research on shortfin mako or in areas of their habitat will be required to obtain permits and/or comply with strict guidelines. This may limit the type and/or duration of research permitted on shortfin mako and may lengthen the preparation time required for planning research projects.
Shipping, oil and gas operations and other marine activities may be impacted by listing shortfin mako under SARA. No specific threats from these or other activities have been identified. However, if these sharks are listed as suggested by COSEWIC, prohibitions will apply to ALL activities affecting these species.
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 shortfin mako (Atlantic population) Isurus oxyrinchus in Canada. Committee on the Status of Endangered Wildlife in Canada. Ottawa. vi + 24 pp.
DFO, 2002. Canadian Atlantic Pelagic Shark Management Plan 2002-2007.
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