Tope (Galeorhinus galeus) COSEWIC assessment and status report: chapter 7

Commercial Fisheries

Historical (1930-1949)

In the early 1930s, tope fisheries in the northeast Pacific were composed of a small fresh fillet market in California and a “substantial” dried fin Asian export market (Ripley 1946; Appendix 1). Prior to 1937 there was no distinction of species in the catch record and therefore the catch shown in Appendix 1 is for all species of shark. Beginning in 1937 tope became the target of a brief but extensive commercial fishery throughout their northeast Pacific range. The fishery began in California and then followed in British Columbia, Oregon, and Washington in the early 1940s (Figure 7). The focus of the west coast tope fishery was for their liver which contains the highest concentrations of vitamin A of any fish on the Pacific coast (Bailey 1952). Prior to World War II, Vitamin A was supplied to the U.S. market processed from Atlantic cod in European waters. The European trade route was greatly curtailed during war times resulting in the rapid development of U.S. based vitamin A sources including the lucrative tope. On average, tope livers contain 4.5 to 20 times more vitamin A per gram then spiny dogfish, the next most important shark that was concurrently being targeted (Bailey 1952). 

By 1939, about 600 vessels were fishing for tope along the entire coast of California (Byers 1940). Prior to 1941 there was no distinction made between species in the California shark catch, and therefore for the purposes of this report the proportion (52.9%) of tope in the total catch after 1941 is applied to the total shark landings pre-1941 as reported in Ripley (1946). Ripley (1946) stated that the post-1941 California landings were minimums as much of the tope catch was still being recorded as unidentified shark. Furthermore, Ripley (1946) pointed out that the percentage of tope in the landings between 1939 and 1941 was undoubtedly higher than in years following 1941. The California landings presented in Figure 7 should therefore be considered minimum estimates. All shark landings from 1930 to the California fishery peaked in 1939 (2209 t) which was before the Canadian fishery for tope had even begun. By 1942 landings of tope in the California fishery had dropped by over 50% and by 1945 the fishery had collapsed. Over 10,000 t were taken over a seven year period which according to Ebert (2003) decimated the population particularly the nursery areas in San Francisco and Tomales Bays.

The Canadian fishery took place primarily off the west coast of Vancouver Island and in Hecate Strait (Figure 6). Fishing took place in about 45 m of water using a variety of fishing gear including halibut longlines, dogfish longlines, trawls, sunken gillnets and driftnets (Barraclough 1948). Sunken gillnets proved to be the most effective technique in Canada although longlines were also commonly used. Preferred longline technique involved using hooks baited with herring, suspended about 2 m from the bottom (Clemens and Wilby 1946).

Figure 7. Estimated catch of tope along the west coast of North Americafrom 1938 to 1949. Data sources: California-Ripley (1946), Canada-Barraclough (1946) and Bailey (1952), Oregon (Westrheim 1950), Washington (Department of the Interior Information Service). California landings pre-1941 based on proportion (52.9%) of total shark landings. Canadian, Washington, and Oregon liver landings converted to whole weights based on conversion from Bailey (1952). See Appendix 1 for values.

Figure 7. Estimated catch of tope along the west coast of North Americafrom 1938 to 1949.

In the early catch statistics only the weight of the liver was reported. The liver comprises approximately 10% of the weight of adult male tope (Bailey 1952). The fishery started off quite small in 1940 with reported liver landings of 1.2 t or approximately 12 t of round fish (Figure 7). By 1942, British Columbia newspapers reported the value of tope livers at between $11-12.80/kg which was approximately 25 times the value of spiny dogfish livers.  In 2006 dollars the value is equivalent to $139-161/kg. By 1944, prices had climbed higher to $20.40/kg (Anon. 1944a). A 1944 fishing article reported that a boat fishing off the west coast of Vancouver Island caught 700 sharks in 17 days producing 2941 kg of liver valued at $20,000 (2006 Present value $215 000) (Anon. 1944b).  The high value fuelled by rising use of vitamin A and cut-off of foreign supplies initiated an all-out bonanza on tope. The British Columbia fishery peaked in 1944 at 278 t or approximately 13,200 individuals.

Note: The total number of individuals is estimated by using the average length of tope in the catch off California (160 cm) (Ripley 1946) and the length-weight relationship Wtkg=2.17x 10-6 (TL)3.17(Olsen 1954) for an average weight per individual of 21 kg. 

By 1944 landings of tope off California had declined by 65% from the 1943 total despite intensified efforts (Anon. 1944a). Canadian fishing magazines were reporting a decrease in Canadian abundance starting in 1944 and by 1946 the Canadian fishery had substantially diminished. In 1947 vitamin A was first synthesized, which removed the demand on natural sources for its procurement. By 1949 the Canadian fishery for tope had ended.

Tope fishing was also carried out by fishers out of Washington and Oregon States along the west coast of the U.S. but also a lot of effort in Canadian waters (Westrheim 1950). Some of the American vessel landings were recorded in Canadian landings due to special circumstances permitted by the War Measures Act (Anon. 1942), but most American vessels landed their livers in U.S. ports. Washington state landings from 1942, 1943, and 1944 are published in U.S. Department of the Interior Information Service press releases available online (http://news.fws.gov/historic/1944/ 19440410.pdf). These records represent the minimum landings of livers in Washington as they only represent three years (Figure 7).

Tope livers landed in Oregon State from 1941 to 1949 are summarized in Westrheim (1950). Landings in Oregon peaked in 1943 with liver landings of 122 t or ~1200 t round weight (Figure 7). It is interesting to note that the Oregon fleet used primarily floating gillnets on average 1.9 km long which apparently was more effective during summer months and were used up to 160 km from shore (Westrheim 1950). The fleet progressed northwards with most of the fleet fishing off of California in April-June and then off of Washington State and British Columbia in August through October.

Based on an approximate weight of 21 kg/shark, a total of approximately 840,000 tope may have been taken from the northeast Pacific population of which about 50,000 were landed in Canadian ports and an unknown amount actually caught in Canadian waters (Appendix 1).

Present-day fishery interactions inU.S.waters

Present-day commercial catches of tope in U.S. waters have been reported since 1976. Catches between 1976 and 1994 have varied between 100–380t whole weight (Walker 1999). In California, landings from 1995 to 1999 varied between 20 and 45 t dressed weight (Ebert 2001) or 30-68 t whole weight based on a conversion factor of 1.5 (Walker 1999). From 2001 to 2004 annual average landings in California waters averaged 21 t (CDFG 2001; 2002; 2003; 2004).

Recreational catches of tope primarily in waters off California are “sketchy at best” and are underreported (Ebert 2001). Tope are still sought for their meat.

Present-day fishery interactions in Canadian waters

There are no directed shark fisheries in Canada’s Pacific waters with the exception of spiny dogfish. Tope are caught in low numbers as bycatch in trawl and longline fisheries while in pursuit of other commercial species. Since 1997 the commercial groundfish trawl fleet has been monitored with 100% at-sea observer coverage. Prior to 2001, reporting of non-commercial elasmobranch species was incomplete in this fishery (McFarlane pers. comm. 2006). Between 2001 and 2005 an average of 651 kg/yr of tope was observed caught by British Columbia trawl fisheries (Figure 8). Assuming an average weight of ~21 kg, a total of 31 tope a year may be caught by the trawl fleet. Most of the catch is from Pacific Marine Fisheries Commission (PMFC) areas 3C/D (Table 2; Figure 3). Tope have been captured in all months of the year with the exceptions of March and April (Appendix 2a, Appendix 2b).

Figure 8. Reported commercial catch (t) of tope in Canada’s Pacific waters by year. Note that hook and line observer coverage represents only 10-15% of the total number of trips. Source: PacHarv database.

Figure 8. Reported commercial catch (t) of tope in Canada’s Pacific waters by year. Note that hook and line observer coverage represents only 10-15% of the total number of trips.
Table 2. Commercial trawl catch (kg) of tope by year and PMFC area in Canada’s Pacific waters based on at-sea observer coverage from 1996 to 2005. Data prior to 2001 is considered incomplete and not included in average. Estimated number of sharks based on a mean weight of 21 kg.
Source: PacHarvTrawl database.
Year Area 3C
Catch (kg)-Trawl
Area 3D
Catch (kg)-Trawl
Area 5A
Catch (kg)-Trawl
Area 5B
Catch (kg)-Trawl
Area 5C
Catch (kg)-Trawl
Area 5D
Catch (kg)-Trawl
Total Estimated
number of sharks
1997
27
24
45
 
 
 
96
5
1999
 
 
 
 
18
 
18
1
2000
94
 
36
 
18
 
148
7
2001
273
82
58
68
29
83
592
28
2002
75
116
263
45
36
27
562
27
2003
200
14
109
101
86
 
509
24
2004
265
254
68
 
 
 
587
28
2005
538
147
56
191
73
 
1004
48
Total (kg)
(1997-2005)
1472
637
635
405
260
110
3516
168
Average (kg)
(2001-2004)
270
123
111
101
56
55
651
31

Beginning in 2000, hook and line fisheries (i.e., halibut, rockfish, lingcod, and spiny dogfish) also started to receive limited observer coverage of between 10-15%. Between 2001 and 2004 an average of 259 kg/yr of tope was observed captured by hook and line fleets (Figure 8; Table 3). An additional amount of 343 kg has been reported in fisher logbooks (Table 3). Because hook and line fleets only receive partial observer coverage (i.e., ~10-15%) the actual catch is larger but presently unknown. As of April 2006 all hook and line licensed vessels operating in Canada’s Pacific waters will be subject to 100% at-sea observer coverage in the form of electronic monitoring. A more accurate understanding of tope catch will be possible with the use of this technology. The mortality rate of the discarded sharks is unknown. Overall, the preliminary observer data indicates that the bycatch of tope in Canadian waters is likely minimal. If the annual observed catch by the hook and line represents ~15% of the actual catch, then perhaps 2 t/yr may be caught by this type of gear with an additional 1 t/yr caught by the trawl fleet for a combined maximum of 3t/yr or ~143 individual tope. The impact of this catch on the population depends on the size of the population which at present time is completely unknown (see Population Sizes and Trends section).

Table 3. Reported catch (kg) of tope in Canada’s Pacific waters by hook and line fleets from observer and logbook programs. Estimated number of sharks based on a mean weight of 21 kg.
Source: PacHarvHL database.
Year HL Observed catch (kg) HL Logbook catch (kg) Estimated number of sharks
2000
 
323
15
2001
250
 
12
2002
92
 
4
2003
693
 
33
2004
0
 
 
2005
 
20
1
Total (kg)
1035
343
66
Average (kg)
259
 
 

Page details

Date modified: