Northern wolffish and spotted wolffish recovery strategy: chapter 2

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Species Information and Evaluation of Current Status

1. Introduction

Wolffish (Family Anarhichadidae), also referred to as catfish by the fishing industry, inhabit a wide range of northern latitudes in the Atlantic and Pacific Oceans (Scott and Scott 1988). Four species of the genus Anarhichas commonly inhabit Canadian waters: A. denticulatus (northern or broadhead wolffish), A. minor (spotted wolffish) and A. lupus (Atlantic or Atlantic Wolffish) in the Atlantic and Arctic Oceans (Barsukov 1959, Templeman 1985, 1986b), and A. orientalis (Bering wolffish) in the Arctic Ocean (Houston and McAllister 1990). The first three species are also distributed in the northeastern Atlantic (Barsukov 1959, Baranenkova et al. 1960) including southeast and southwest of Greenland, (Möller and Rätz 1999, Stransky 2001), the latter contiguous with Canadian waters. The west Greenland components (A. lupus and A. minor) underwent a decline similar in magnitude and timing to the decline in Canadian waters while the east Greenland component did not (Möller and Rätz 1999). Reported catches off west Greenland have not exceeded 100 t in recent years. All three species extend into USA waters, but there they are uncommon (A. lupus) or rare (A. minor and A. denticulatus).

Kulka and DeBlois (1996) described the distribution of the three species off eastern Newfoundland as quite extensive, inhabiting most of the Labrador and northeast Newfoundland Shelves (less so in recent years) to the southern Grand Banks and Flemish Cap (Figure 1). The northern limit of all three species occurs in the Davis Strait. Research surveys on the Scotian Shelf and in the Gulf of St. Lawrence regularly take both A. denticulatus and A. minor, but at much lower rates than in the Grand Banks to Labrador Shelf region. This would indicate that the former regions represent the southern fringe of distribution for these two wolffish species. A. lupus differed from the other two species in that they are densely concentrated on the shallow part of the southern Grand Bank (Kulka and DeBlois 1996). A. lupus is also common in the deeper parts of the Gulf of St. Lawrence, on the Scotian Shelf, in the Bay of Fundy (McRuer et al. 2001) and Gulf of Maine/Georges Bank (Nelson and Ross 1992).

Through tagging studies, Templeman (1984) suggested that wolffish are largely sedentary, undergoing limited migration with most recaptures occurring within 8 km of the tagging site. Kohler (1968) and Keats et al. (1985) reported seasonal movement inshore by A. lupus. The broad distribution observed for the three species coupled with limited movement as reported by Templeman (1984) suggests the possibility of the existence of Evolutionary Significant Units (ESU’s), also referred to as Designatable Units (DU’s) or sub-populations. Work is under way to establish whether this is the case.

Wolffish fall into relatively “low” productivity category based on growth, fecundity and age characteristics of A. lupus in USA waters as described by Musick (1999). The testes of these species are relatively small, sperm and egg production is low, fertilization is internal, and eggs and larvae are large. Wiseman (1997) reports that newly hatched larvae of A. lupus are about 2 cm in length. Although fecundity is low, internal fertilization (Pavlov 1994), nesting habits and egg guarding behaviour in A. lupus (Keats et al. 1985) effectively increases potential for survival of individuals during the early life stages. A. lupus in Newfoundlandwaters spawn in September and the entire larval stage is spent close to the hatching location (Templeman 1985 and 1986a). Information on A. minor and A. denticulatus is more limited, but A. denticulatus appears to spawn in late fall or early winter (Templeman 1985 and 1986a). Nesting and egg guarding has not been observed for the either A. denticulatus or A. minor.

Details of wolffish life history in Canadian Atlantic waters are sparse, perhaps because it is not the target of a commercial fishery. Templeman (1984, 1985, 1986a, 1986b) and Albikovskaya (1982) examined certain aspects of its biology. Kulka and DeBlois (1996) and Simpson and Kulka (2002) described abundance and distribution. McRuer et al. (2001) examined fish sizes and maturity in addition to abundance and distribution of A. lupus on the Scotian Shelf and in the Gulf of St. Lawrence. However, many knowledge gaps remain. In particular, no age dis-aggregated studies have been carried out for the northwest Atlantic but age-length relationships are established for the northeast Atlantic (Shevelev 1995). Natural and fishing mortality in the Barents Sea (Shevelev 1992), migration (Riget 1986) and distribution and abundance off west Greenland (Riget and Messtorff 1987, Messtorff 1986) have been examined. The aquaculture potential of the two species (A. minor and A. lupus) has been examined through egg rearing (Falk-Petersen and Hansen 1994), growth rate (Moksness 1994, Moksness and Stefanussen 1990) and feeding (Orlava et al. 1989a, b) experiments.

Wolffish have been exploited in a directed fishery off Greenland (Mõller and Ratz 1999, Smidt 1981), but within Canadian waters they have only ever comprised bycatch. Kulka (1986) reported on bycatch levels of the three species in Canadian waters. It was noted that annually during the 1980s, about 1,000 t of the three species (combined) were caught in many fisheries directed for other species. About half of the A. minor and A. lupus caught was landed and all of A. denticulatus were reported as discarded. Information on distribution presented by Simpson and Kulka (2002) and Kulka and DeBlois (1996) indicate a potential for overlap of fisheries with the distribution of wolffish species outside 200 miles on the Grand Banks and the Flemish Cap. However, most data on catches of these species outside 200 miles are not accessible.

With the decline in the traditional groundfish (demersal species) resources in the waters around Newfoundland and Labrador, in the early 1990s, interest in the exploitation of alternate species increased. A. minor and A. lupus had been considered in the mid-1990s as potential candidates for new directed fisheries. However, experimental fishing did not identify areas where catch rates were sufficiently high to warrant directed commercial exploitation. This finding was consistent with studies that indicate wolffish do not form dense concentrations (Templeman 1986a, Kulka and DeBlois 1996, Simpson and Kulka 2002).

Kulka and DeBlois (1996) and Simpson and Kulka (2002) noted a significant decline in research trawl survey indices (numbers and weights) of the three species starting in the late 1970s and early 1980s. While all three species have undergone a substantial decline during the 1980s-1990s, the proximal cause remains uncertain. These declines in abundance were concurrent with a widespread reduction in abundance of many groundfish species from the Grand Banks to the northern Labrador Shelf.

In 2001, two species, A. denticulatus and A. minor were assessed by COSEWIC (Committee on the Status of Endangered Wildlife in Canada) as “threatened”. This assessment refers to species likely to become “endangered” if limiting factors are not reversed, while “endangered” refers to species facing imminent extirpation or extinction. The unpublished COSEWIC status reports indicated that abundance of the two species had declined by greater than 90% over three generations, the extent of their distribution had decreased, and threats included mortality as bycatch in commercial fisheries and habitat alteration by bottom trawling. The third species, A. lupus was assessed as “special concern” (a species which may become a threatened or an endangered species because of a combination of biological characteristics and identified threats). All three wolffish species where included in Schedule 1 of the Species at Risk Act (SARA) at the time of the Act’s proclamation in June 2003.

This document outlines a strategy for the recovery of A. denticulatus and A. minor, and a management plan for A. lupus. The purpose of this document is to lay out a roadmap for scientists, managers and other stakeholders to promote the recovery of wolffish.

1.1 Species Information and Evaluation of Current Status

1.1.1 Species Information: Northern Wolffish

Common Name: Northern wolffish, Broadhead wolffish, Bullheaded wolffish, Catfish

Scientific Name: Anarhichas denticulatus

Assessment Summary: 2001 (New)

Status: Threatened (SARA Schedule 1)

Reason for Designation: Numbers of this large, slow-growing, long-lived, solitary, nest-building fish have declined over 95% in three generations, and the number of locations where the fish is found has decreased. Apparent threats may include mortality as a result of bycatch and habitat alteration by bottom trawling, ocean dumping and pollution, perhaps compounded by environmental change. Dispersal is limited (COSEWIC unpublished).

Canadian Occurrence: Arctic Ocean, North Atlantic Ocean

Status History: Assessed as threatened by COSEWIC in May 2001.

1.1.2 Species Information: Spotted Wolffish

Common Name: Spotted wolffish, Leopardfish, Catfish

Scientific Name: Anarhichas minor

Assessment Summary: 2001 (New)

Status: Threatened (SARA Schedule 1)

Reason for Designation: Numbers of this large, slow-growing, long-lived, solitary, nest-building fish have declined over 90% in three generations, and the number of locations where the fish is found has decreased. Apparent threats may include mortality as a result of bycatch and habitat alteration by bottom trawling, ocean dumping and pollution, perhaps compounded by environmental change. Dispersal is limited (COSEWIC unpublished).

Canadian Occurrence: Arctic Ocean, North Atlantic Ocean

Status History: Assessed as threatened by COSEWIC in May 2001.

1.1.3 Species Information: AtlanticWolffish

Common Name: Atlantic Wolffish, and Catfish

Scientific Name: Anarhichas lupus

Assessment Summary: November 2000 (New)

Status: Special Concern (SARA Schedule 1)

Reason for Designation: Numbers of this large, solitary, slow-growing, late-maturing, egg-guarding benthic fish have declined significantly since the 1970s, over a part of its range. Apparent threats are perhaps related to fishing and habitat alteration, ocean dumping, pollution, perhaps compounded by environmental change (COSEWIC unpublished).

Canadian Occurrence: North Atlantic Ocean

Status History: Assessed as Special Concern by COSEWIC in November 2000. Assessment based on a new status report.

1.1.4 General Description of Family Anarhichadidae

Wolffish (Family Anarhichadidae) are elongated fish inhabiting a wide range of northern latitudes and depths in the Atlantic, Pacific and Arctic Oceans (Scott and Scott 1988). They are named for their large powerful jaws with noticeable conical (canine-like) anterior teeth and large lateral molariform teeth used to crush various invertebrate prey (Rodriguez-Marine et al. 1994; Albikovskaya 1983). They have a soft rayed dorsal fin, a small caudal fin, large fan-like pectoral fins and no pelvic fins (Scott and Scott 1988).

Distinguishing features of the three Atlantic species are as follows. A. denticulatus is more evenly coloured (dark) with a large head in proportion to the body, hence the alternate name, broadhead wolffish. Templeman (1986b) also described a rarely occurring spotted form of A. denticulatus, some of which were previously suggested to be inter-specific forms between A. lupus, and A. minor (Luhmann 1954). A. minor is spotted and darker coloured from pale olive to chocolate brown and A. lupus is grey with vertical bars along most of its body length. The most recent information on the biology, distribution and status of wolffish in Canadian Atlantic waters can be found in McRuer et al. (2001) for the Gulf of St. Lawrence and Scotian Shelf, and Simpson and Kulka (2002) for the Grand Banks, northeast Newfoundland Shelf and Labrador Shelf. Life history characteristics of the three species are summarized in Table 1. Wolffish are widespread, but do not form dense concentrations sufficient to support a significant commercial fishery. Thus there is no directed fishery for these species in Atlantic Canada. However, all three are common bycatch in various fisheries. A. minor and A. lupus were sometimes retained for market.

Table 1. Comparison of essential life history characteristics of three Anarhichas species found in eastern Canadian waters. F = female, M = male. References cited below as superscript are found, similarly superscripted in Literature Cited.