COSEWIC Assessment and Status Report on the Porbeagle Lamna nasus in Canada - 2014

Committee on the Status of Endangered Wildlife in Canada (COSEWIC) status reports are working documents used in assigning the status of wildlife species suspected of being at risk. This report may be cited as follows:

Previous report(s):
Crossman, E.J.1994. COSEWIC status report on the Status of Endangered Wildlife in Canada. Committee on the Status of Endangered Wildlife in Canada. Ottawa. viii + 43 pp. (www.sararegistry.gc.ca/status/status_e.cfm).

For additional copies contact:

COSEWIC Secretariat
c/o Canadian Wildlife Service
Environment Canada
Ottawa, ON
K1A 0H3

Tel.: 819-953-3215
Fax: 819-994-3684
COSEWIC E-mail
COSEWIC web site

©Her Majesty the Queen in Right of Canada, 2014.

Catalogue No. CW69-14/388-2014E-PDF
ISBN 978-1-100-23961-3

Porbeagle occurs in temperate waters in the North Atlantic, South Atlantic, South Pacific, South Indian and Antarctic Oceans. In the Northwest Atlantic, it ranges from northern Newfoundland and Labrador to New Jersey and possibly South Carolina, with mature females ranging farther south to the Sargasso Sea. It is widely distributed in the Canadian Atlantic and is found in the Gulf of St. Lawrence, around Newfoundland and Labrador, on the Scotian Shelf and in the Bay of Fundy. Most of the population in the Northwest Atlantic is within Canadian waters.

Porbeagle is a cold-water species, occurring from coastal areas to the open sea, most often on continental shelves. In Canadian waters, it is encountered primarily in the deeper basins and along the shelf edge in depths less than 200 m and temperatures between 5-10°C. Mating grounds include the Grand Banks off southern Newfoundland and Labrador and Georges Bank, and pupping grounds are located in the Sargasso Sea. Porbeagle is among the deepest diving of pelagic sharks, with a maximum recorded depth of 1,360 m.

Adult females breed every year, with a gestation period of 8-9 months. In the Northwest Atlantic, they mate in the summer and early fall, and females give birth in the late winter or early spring. Litter size ranges from 2-6 pups, with an average of 3.9. Porbeagle has slow growth and late maturity, with length and age at 50% maturity of 174 cm and 8 years for males, and 217 cm and 13 years for females. These fish grow rapidly in their first year, and in the Northwest Atlantic they recruit into the fishery at age 0-1. Age has been validated up to 26 years, but they may live for more than 40 years. Natural mortality has been estimated to range from 0.10-0.20, and the generation time is 18 years.

Porbeagle is a warm-blooded shark. The presence of a vascular heat exchange mechanism allows individuals to maintain a body temperature around 7-10°C higher than ambient water temperature. They are opportunistic predators, feeding on a wide variety of prey, including fish and cephalopods.

Movement and migratory patterns of Porbeagle in the Northwest Atlantic are extensive and consistent from year to year. The fish appear in the Gulf of Maine and around the southern Scotian Shelf in late winter, move northeast to offshore basins in the spring, and reach the southern coast of Newfoundland and Labrador and the Gulf of St. Lawrence in the summer and fall. A return movement to the southwest occurs in late fall, with mature females migrating farther south to the Sargasso Sea in the winter.

The total 2009 Porbeagle abundance has been estimated to be approximately 197,000-207,000 individuals, including about 11,000-14,000 spawning females. The total population biomass was estimated to be 10,000 metric tonnes for the same year. Since 1961, the abundance of spawning females and total abundance have declined by about 74-77% and 56-70%, respectively. Population decline appears to have halted over the past decade, as fisheries were reduced. Population recovery has been predicted to occur on the order of decades if incidental mortality rates are kept less than 4% of the vulnerable biomass.

Overfishing of Porbeagle in the Northwest Atlantic in the 1960s and again in the 1990s led to two successive population collapses. In Canada, landings were first restricted by quotas in 1998, and were less than 100 tonnes annually from 2009 to 2011. The directed fishery was discontinued in 2013. However, Porbeagle is still taken as bycatch in swordfish and tuna longline fisheries, and in groundfish longline fisheries, gillnet and bottom trawl fisheries. In Atlantic Canada, Porbeagle discards remain unrecorded in most of the fisheries statistics, except for those collected by Canadian Fisheries Observers. There is little information on Porbeagle catches outside Canada. Unknown and unregulated catches may undermine population recovery.

In Canada, Porbeagle is managed based on stock assessments, and directed fishing was not permitted in 2013. In 2004, COSEWIC assessed Porbeagle as Endangered using criterion A2bd, though it was not listed under the Species at Risk Act (SARA) because of economic losses associated with eliminating the directed fishery. Reduced catch levels were thought to be low enough to avoid jeopardizing the long-term recovery of the species. The World Conservation Union (IUCN) lists Porbeagle as Vulnerable (A2bd+3d+4bd) because of its low reproductive capacity and high commercial value. In 2013, Porbeagle was listed on Appendix II of the Convention on International Trade in Endangered Species of Wild Flora and Fauna (CITES).

Since the preparation of the previous COSEWIC status report on Porbeagle in 2004 (COSEWIC 2004), several new studies have been conducted on Porbeagle in the Northwest Atlantic Ocean. A satellite tracking study has identified a Porbeagle pupping ground in international waters, with mature females migrating as far as 2,356 km south to the Sargasso Sea in winter to give birth there in the spring. The same study also found Porbeagle to be among the deepest diving of pelagic sharks, and recorded mature females at depths of up to 1360 m. Catches of Porbeagle in Newfoundland and Labrador waters have indicated that its range extends slightly farther north along the coast than documented in the previous COSEWIC report. This in part has resulted in the extent of occurrence of Porbeagle increasing from 1,210,000 km2 to 1,313,086 km2. In 2006, the IUCN changed its listing of Porbeagle from Lower Risk/Near Threatened to Vulnerable. In 2013, Porbeagle was listed on Appendix II of CITES. The directed fishery for Porbeagle in Canada was not permitted in 2013.

The Committee on the Status of Endangered Wildlife in Canada (COSEWIC) was created in 1977 as a result of a recommendation at the Federal-Provincial Wildlife Conference held in 1976. It arose from the need for a single, official, scientifically sound, national listing of wildlife species at risk. In 1978, COSEWIC designated its first species and produced its first list of Canadian species at risk. Species designated at meetings of the full committee are added to the list. On June 5, 2003, the Species at Risk Act (SARA) was proclaimed. SARA establishes COSEWIC as an advisory body ensuring that species will continue to be assessed under a rigorous and independent scientific process.

The Committee on the Status of Endangered Wildlife in Canada (COSEWIC) assesses the national status of wild species, subspecies, varieties, or other designatable units that are considered to be at risk in Canada. Designations are made on native species for the following taxonomic groups: mammals, birds, reptiles, amphibians, fishes, arthropods, molluscs, vascular plants, mosses, and lichens.

COSEWIC comprises members from each provincial and territorial government wildlife agency, four federal entities (Canadian Wildlife Service, Parks Canada Agency, Department of Fisheries and Oceans, and the Federal Biodiversity Information Partnership, chaired by the Canadian Museum of Nature), three non-government science members and the co-chairs of the species specialist subcommittees and the Aboriginal Traditional Knowledge subcommittee. The Committee meets to consider status reports on candidate species.

A species, subspecies, variety, or geographically or genetically distinct population of animal, plant or other organism, other than a bacterium or virus, that is wild by nature and is either native to Canada or has extended its range into Canada without human intervention and has been present in Canada for at least 50 years.

The Canadian Wildlife Service, Environment Canada, provides full administrative and financial support to the COSEWIC Secretariat.

The extent of occurrence (EO) of Porbeagle in Canadian waters is 1,866,975 km2 (Figure 4). When excluding land, the EO is 1,313,086 km2. These values are larger than the EO calculated for Porbeagle in its previous COSEWIC assessment, which was 1,212,000 km2 (COSEWIC 2004). The index of area of occupancy (IAO) was estimated as the surface area of grid cells (2 km x 2 km) that intersect the mating grounds plus the capture locations of gravid females (Figure 5). IAO was estimated as 77,576 km2 (based on 19,394 grids). EO and IAO were calculated based on capture locations from fisheries data. It is important to note that IAO is likely an underestimate as it is only based on the grid cells where Porbeagle has been caught, and the fishery did not cover the entire extent of the species’ distribution.

Simpson and Miri (2013) provided updated catch information for Porbeagle in Newfoundland and Labrador waters. This included catch locations from fishery-independent surveys (conducted since 1946) and from fisheries observers deployed from the Newfoundland and Labrador region.

Trends in habitat for Porbeagle are not known, but there is little evidence to suggest that suitable habitats have decreased or deteriorated. A wide distribution, opportunistic diet and long migrations suggest that Porbeagle is a flexible and adaptable species.

Generation time, which is the average age of parents in the current cohort, is estimated as the age at which 50% of the females are mature + 1/M, where M is the instantaneous rate of natural mortality. Therefore, generation time is 18 years (13 + 1/0.2).

Table 1. Table providing estimates of spawning female abundance and total population abundance by year (1961 to 2009) obtained from four models fitted to Porbeagle data. The models indicate that the 2009 population is at about 22 to 27 percent of its size in 1961 and 95 to 109 percent of its size in 2001, with spawning female abundance at about 12 to 16 percent of 1961 levels and 83 to 103 percent of 2001 levels.

The percent change in population size was calculated since the beginning of exploitation in 1961 until 2009 (~2.6 generations or 48 years). This calculation was calculated as 100(exp(y b) – 1), where y is the number of years in the time series and b is the slope of the regression. Spawning females declined by 74-77% over this period, and the total population declined by 56-70% (Table 2). These declines appear to have stopped in 2004-2006 (Table 1).

Table 2. Table summarizing natural log regression parameters of the logged abundance of all individuals and of spawning females calculated from each of four models fitted to Porbeagle data presented in Campana et al, 2012.

Porbeagle in the Northwest Atlantic appear to be reproductively independent of the population in the Northeast Atlantic. Thus, there is no rescue potential from fish in the eastern Atlantic. Fish in the Northwest Atlantic undertake extensive movements along the east coast of Canada and the US, and approximately 80-90% of the population occurs in Canadian waters. Thus, it is unlikely that fish from the Canadian side of the population would be rescued from the much smaller number of fish currently restricted to US waters.

Porbeagle are highly migratory and distributed continuously throughout their range in the Northwest Atlantic. In Canada, the greatest current threat to Porbeagle is overfishing due to multiple bycatch fisheries, which are not closely monitored, where a large portion of the catch may be discarded and unreported. Therefore, it is difficult to apply the IUCN/COSEWIC definition of number of locations to this species.

In the US, Porbeagle is managed under the Highly Migratory Species Fisheries Management Plan (http://www.nmfs.noaa.gov/sfa/hms/hmsdocument_files/FMPs.htm). Restrictions include trip and gear limits, weight quotas, minimum size landings and finning bans (NOAA 2011). There are also time/area closures for pelagic longliners. Porbeagle was listed as a Species of Concern in 2006 and in 2010 the National Marine Fisheries Service received two petitions to list Porbeagle under the Endangered Species Act (ESA). However, neither petition succeeded, so Porbeagle has not been listed on the ESA (NOAA 2011).

There are currently some measures in place for managing Porbeagle fishing in international waters. In 1999, the United Nations Food and Agricultural Organization developed an International Plan of Action (IPOA) for the Conservation and Management of Sharks, which is a voluntary protocol designed to ensure the conservation and management of sharks and their long-term sustainable use (FAO 1999). In cooperation with the IPOA, bodies in the North Atlantic such as the International Council for the Exploration of the Sea, the International Commission for the Conservation of Atlantic Tunas and NAFO have initiated efforts encouraging member countries to collect information about sharks, including Porbeagle (FAO 1999).

In March 2013 at the 16th Conference of the Parties, Porbeagle was accepted for inclusion on Appendix II of CITES (http://www.cites.org/eng/news/pr/2013/20130314_cop16.php), following two previous unsuccessful attempts. DFO is planning to produce its Non-Detriment Findings (NDF) in June 2014, which will examine the science, management and enforcement surrounding the export of the species (Shaw pers. comm. 2014). The implications of the CITES listing will not be known until the NDF is produced.

The population status of Porbeagle has not yet been ranked globally (G rank) or nationally (N rank) in Canada (www.natureserve.org). It also has not been ranked subnationally (S rank) by any Canadian province or territory, except Quebec. Quebec recently changed the subnational rank for Porbeagle from an S4 to an S3S4 (Gauthier pers. comm. 2012), with S4 meaning “apparently secure” and S3 meaning “vulnerable”. Porbeagle is likely to be designated as threatened or vulnerable in Quebec (Éditeur officiel du Québec 2010). The current Canadian and Atlantic General Status rank for Porbeagle is 1, meaning that Porbeagle is considered as an At Risk species by the Canadian Endangered Species Conservation Council (CESCC 2006).

Existing marine protected areas do not offer any significant protection to this species because they cover less than 1% of the species’ range, and individuals are highly migratory. There have been five small marine protected areas (MPAs) established on the east coast of Canada since 2004 that fall within the range of Porbeagle population in the Northwest Atlantic (http://www.dfo-mpo.gc.ca/oceans/marineareas-zonesmarines/mpa-zpm/index-eng.htm). Four of these are along the coastlines of New Brunswick, Prince Edward Island and Newfoundland and Labrador, and are small in size (<100 km2 total area). The fifth is an area of 2,634 km2 in the Gully, which is a deep canyon ecosystem at the edge of the Scotian Shelf near Sable Island, about 200 km offshore from Nova Scotia. This larger protected area comprises three management zones, one of which prohibits pelagic longlining. Six additional areas/habitats (coastal and offshore) have been labelled as Areas of Interest for future designation as MPAs along Canada’s east coast. Porbeagle has also been documented in the St. Lawrence Estuary in close proximity (a few km upstream) to the Saguenay-St. Lawrence Marine Park, at La Malbaie (Paradis pers. comm. 2012).

The report writer gratefully acknowledges Steve Campana for access to Porbeagle data and assessment information, for discussions about the population and the fishery, and for answering questions. The report writer also thanks the following people for assisting in the preparation of the report: Joseph Pratt and Stephen Turnbull (University of New Brunswick) and Mary Sabine (Department of Natural Resources New Brunswick) for data and information on Porbeagle in New Brunswick waters and the Bay of Fundy; Mark Simpson (DFO) for data and information on Porbeagle in Newfoundland and Labrador waters; Mike Eagles and Jennifer Shaw (DFO) and Isabelle Gauthier and Annie Levesque (Ministère des Ressources naturelles et de la Faune du Québec) for information and updates regarding the protection status and management of Porbeagle; Stefen Gerriets (Atlantic Canada Conservation Data Centre), Donald McAlpine (New Brunswick Museum) and Briar Howes and Sylvain Paradis (Parks Canada) for catch locations and distribution information; Henrik Larsen (International Council for the Exploration of the Sea) for access to Porbeagle literature; Jenny Wu (COSEWIC Secretariat) for preparation of the Canadian range map and for helping with range calculations; Julie Perrault (COSEWIC Secretariat) and Alan Sinclair (COSEWIC) for discussions and advice on COSEWIC status reports and assessments. The author acknowledges Julia Baum for writing the original COSEWIC status report on Porbeagle and the Sea Around Us Project for providing support for this one.

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Appendix 1. Table of annual reported landings (metric tonnes) of Porbeagle by country for NAFO Subareas 2 to 6, from 1961 to 2008

Notes:

Northwest Atlantic data for 1950-1960 are from FAO (ICCAT Report of Shark Working Group, Miami, 26 - 28 February 1996), 1964-1986 from NAFO, 1987-2004 from Scotia-Fundy and NF IOP (includes landings and discards), and 2000-2008 from FAO Fishstat Plus v 2.32 Capture Production March 2008, NAFO Database 21B or ICCAT Task 1 Dataset 2009
Canada data for 1961-1990 are from NAFO, 1991-2002 from DFO Zonal Statistics File, corrected to appropriate live equivalent weight, and 2003-2008 from DFO MARFIS
Faroe Island data for 1961-1963 are from FAO (ICCAT Report of Shark Working Group, Miami, 26-28 February 1996)
France data are from FAO Statistics (1998), 2000-2006 from FAO Fishstat Plus v 2.32
Northwest Atlantic data for 2000-2006 (Japan) are from NAFO Database 21B, catch for code 469, large sharks
Norway data for 1961-1986 are from NAFO
NAFO catch data for Spain for 2005 (231mt) and 2006 (230 mt) were errors, and not reported here
Northwest Atlantic data for US from 1961-1994 are from FAO (ICCAT Report of Shark Working Group, Miami, 26-28 February 1996)