THE FISHERMAN, NOVEMBER 23, 1998
Fleet praised for coho conservation
Fishermen saved coho by the thousands this year — and the numbers now emerging from DFO computers show just how well they did it.
Conservation measures carried out this tear by the fleet cut coho exploitation rates on the North Coast to less than one per cent and cut mortality on the south coast just as dramatically.
DFO biologists Bill Shaw and Dave Peacock presented the department's first cut of statistics at the two-day selective fishing workshop in Richmond Nov. 4 and 5. The figures are still preliminary but they already show clearly that the all three gear sectors were successful in getting more coho up to the gravel in 1998.
"The effort everybody put into this year was tremendous," Shaw told the 200 fishermen, DFO and industry representatives at the workshop. "I congratulate all of you."
In statistics for the South Coast, the gillnets were by far the most
North Coast Coho Exploitation Rates
Estimates of Coho Encounters and Mortalities (estimates until Oct. 24/98)
COMMERCIAL Total Coho Encounters Estimated Coho Mortalities Preliminary Catch Estimates (pieces) Non-Coho Total Coho released To Fish Kept Ratio
Sockeye Pink Chum Chinook
Troll - Area G Troll - Area H 7,340 1,252 1,980 326 219,000 21,400 990 2,300 128,500 18,000 86,100 450 243,690 233,050 0.03 0.01
Troll Sub Total 8,592 2,234 347,500 39,400 87,090 2,750 476,740 0.02
Seine - Area B 9,156 3,614 456,000 51,225 1,635,771 139 2,143,135 0.004
Seine Sub Total 9,156 3,614 456,000 51,225 1,635,771 139 2,143,135 0.004
Gillnet - Area D Gillnet - Area E 1,610 90 966 54 229,417 13,304 199,091 145 234,000 0 148,995 3,673 441,957 386,668 0.004 0.002
Gillnet Sub Total 1,700 1,020 463,417 13,304 348,086 3,818 828,625 0.002
Commercial Total 19,448 6,868 1,266,917 103,929 2,070,947 6,707 3,448,500 0.006
successful in avoiding coho while the seine and troll sectors managed a higher survival rate on returning coho to the water (see table above).
Fishery Zone Coho Exploit, rate, avg. 90-97 1998 Exploit, rate
Area 3 gn, sn yellow 5% 0.06%
Area 4,5 gn, sn yellow 5% 0.34%
selective seine red no rate <0.01 %
selective trap red no rate 0%
troll 1,3,5 closed 20% 0%
troll 2W, Central yellow <1% <0.1%
Shaw noted that catches of coho in the past, during targeted fisheries off the West Coast of Vancouver Island have been as high as 3.4 million and have averaged 2.2 million between 1970 and 1996. "This year, we moved essentially to zero," he said.
The drop in catch will also mean that Washington and Oregon will benefit from a pass through of their coho stocks.
Peacock's statistics from the North Coast outlined only overall exploitation rates of North Coast coho but the contrast with previous years was stark (see table at left).
What made it particularly remarkable was that it was achieved despite a high abundance of coho on the North Coast, Peacock said.
"The average exploitation rate on coho in Canadian fisheries has been 31 per cent," Peacock said. "This year it was 0.51 per cent."
"We've basically removed the exploitation rate in Canadian fisheries."
There was no reduction in the exploitation rate in Alaska's fisheries which traditionally take about one-third of North Coast coho. While Canadian fishermen were
conserving coho, Peacock said, "it was business as usual in Alaska."
DFO also carried out an experimental seine fishery in the red zone in which coho mortalities averaged five per cent for the 20 boats working the pool fishery.
However, that five per cent mortality figure was only achieved when fishermen were working the area at the mouth of the Skeena and were brailing, Peacock noted. When the boats moved out into the area where the commercial fishery is conducted and ramped the fish aboard, the mortality rates rose to 23 per cent.
$700,000 spent on Alberni Inlet tests
Much of DFO's budget for selective fishing went into a $700,000 experiment in Alberni Inlet in Barkley Sound to test the effectiveness of gear modifications across all three gear sectors in reducing coho mortalities.
Six seiners and six gillnetters took part in the first part of the program, from Sept. 10-16, followed by six trailers, whose test fishery ran from Sept. 22-26. Organized by DFO together with the Industry Selectivity Committee, the objective was to develop new fishing techniques or gear modifications that would either reduce bycatch or increase the survival rates of those that were caught.
DFO stock assessment biologist Brent Hargreaves, who headed up the study, acknowledged that a major deficiency of the study was that it was not in an area where there is a commercial fishery. In addition, because of the late timing, there was an abnormally high abundance of coho, with some boats catching as much or more coho as sockeye.
(On alarming statistic the DFO turned up during the test was a catch of 99 Atlantic salmon — "an amazingly high number," said Hargreaves.)
The experiment was to have taken place in Johnstone Straits during the last week of August but was pulled because of the department's concerns over sockeye migration timing.
The experiment's design gave
to a netpen and held for two or three days before being released.As well, some 7037 fish were tagged and monitored as they migrated through the fishway at Stamp River falls.
"There were a lot of things in
Still to come is the long term post-release survival rate which should be available once all the fish have passed through the fishway and tags have been recovered.
As for gear modifications, the experiment showed that the seiners
MORTALITY RATES, ESTIMATED AND ACTUAL
Gear DFO estimated mortality rate Mortality rate at catch Further mortality in netpen Total
GILLNET 60% 37.4% 15.2% 52.6%
SEINE 25% 0.1% 7.1% 7.2%
TROLL 26% 2.9% 16.3% 19.2%
the most emphasis to the seine fleet which was testing three new pieces of modified gear — a sock brailer, a side purse brailer and a modified seine net with "selectivity grids" that allow juvenile and smaller fish to escape.
Gillnet tests focussed on net soak times and hang ratios while trailers were testing only the effectiveness of live release techniques, with and without revival tanks.
The one advantage of the test site was that it was a terminal area, giving biologists an opportunity to test post-release survival rates. A number of the coho caught in the various fisheries were transferred
this experiment," Hargreaves said.
The results across all sectors showed that the seines caught the most coho although their live release rates were the best (see table). Netpen mortalities increased the overall mortality rate in every sector although the increase was greatest in the troll sector (see table 2).
Still, said Hargreaves, "the mortality rates in every case were lower than what we use for fisheries management." DFO has traditionally pegged the mortality rate for the seine sector at 25 per cent, the gillnets at 60 per cent and trailers at 26 per cent.
using modified gear produced results that were not much different from the "control" group — seiners using a regular brailer—or those ramping the fish aboard. Fishing Vessel Owners Association president Bob Rezansoff, who was using a modified bunt with plastic grids sewn into it, did cut mortalities almost to zero, "but none of the experimental techniques produced results that were significantly different from the control group," Hargreaves noted.
Rezansoff told workshop participants that the selectivity grids were developed for the Juan de Fuca fishery where the fleet
encounters a lot of juvenile coho and chinook.
In the gillnet experiments, changes in the "hang ratio" — the length of gillnet web relative to corkline length — made little difference but the soak time had a significant effect on coho mortalities, Hargreaves said. The mortality rate went down as the soak time was reduced, with 30-minute sets producing the lowest mortalities.
Hargreaves noted that in the troll sector, the catches were too low to produce definitive results, since the total catch for the six boats was only 380 coho. Still, the test did show that the trailers' preferred method of cutting the leader to release the fish without bringing them aboard was effective in reducing mortalities.
"We've still got a lot of work yet to do," said Hargreaves, noting that biologists are still working on blood and tissue samples collected during the test fishery and are continuing to collect data from tagged fish.
The final stage , he said, will be to check fish on the spawning grounds and in the hatchery to get an idea of the long-term survival of fish and their spawning rates after release.