SHRIMP EXPLORATION ON THE BRITISH COLUMBIA COAST 1967 BY M.S.SMITH AND T.H.BUTLER FISHERIES RESEARCH BOARD OF CANADA BIOLOGICAL STATION , NANAIMO B.C. CIRCULAR NO.85 FEBRUARY 1968 ~ < SHRIMP EXPLORATION ON THE BRITISH COLUMBIA COAST 1967 BY M.S.SMITH AND T.H.BUTLER FISHERIES RESEARCH BOARD OF CANADA BIOLOGICAL STATION , NANAI MO B.C. CIRCULAR NO.85 FEBRUARY 1968 INTRODUCTION The Fisheries Research Board of Canada, with the aid of funds provided by the Industrial Development Service of the Department of Fisheries, con- f . tinued to carry out exploration for new shrimp grounds in 1967. Two observers ^ from the Biological Station at Nanaimo, British Columbia, were aboard a ^ . chartered vessel from July 4 to September 9, 1967. The objective of the survey was to find concentrations of shrimp on the outer continental shelf of British Columbia. The programme, consisted of studying areas considered to have commercial potential and re-assessing the potential of grounds found in past shrimp explorations. VESSEL AND EXTENT OF SURVEY The commercial trawler M.V. Ocean Traveller, under Captain Frank Gale, was chartered to carry out the programme. The vessel is a conventional wooden-hulled combination vessel of 80 gross tons (63 ft keel length) powered by a 220 hp diesel engine. Deck equipment included a hydraulic powered combination seine-trawl winch and a hydraulic net reel, conven tionally rigged for double gear trawling* Each winch drum carried approximately 400 fathoms of 9/16" galvanized wire. Auxiliary equipment included an Ekolite 9B sounder, radar, loran and radios. (This was the same captain and vessel that conducted the Industrial Development Service exploratory groundfish surveys in.1965 and 1966). The areas explored in this survey were Estevan Sound to Nepean Sound, Caamano Sound, Surf Inlet, Laredo Sound, the area off Milbanke Sound explored in 1966; Johnson Channel, the SE edge of "Goose Island Grounds"; Fitz Hugh Sound and its approaches; Smith Sound; "the Stump Ranch" (seaward from Virgin Rocks), Queen Charlotte Strait, off Triangle Island; Quatsino Sound and Nootka Sound. During periods of inclement weather when offshore trawling was not feasible various inlets were sounded. On the accompanying map (Fig. 1) the areas covered in this programme can be seen as the shaded portion* FISHING GEAR Prospecting was carried out with a 70-ft Gulf of Mexico heavy duty semi-balloon trawl. A light groundline of plastic and rubber rollers was attached to the footrope of the riefe. A plan of the trawl with specifica tions is shown in Fig. 2, A half section of the groundline is described in Fig. 3. The net and otter boards were rigged similarly to a conventional groundfish trawl. Method of rigging is illustrated in Fig. 3. These are the otter boards used in the 1966 survey. - 2 - Double gear trawling was used; one wire from each winch drum ran through its respective stern davit and was attached to the chain bridle of the otter board. The towing speed was approximately 2 knots. The trawl did not appear to operate satisfactorily during the first six tows and subsequently the chain bridle that was attached to rear points of the doors was substituted for one of %" galvanized cable, and relocated on the rear quarters of the otter boards (see Fig. 3). After this modification the otter boards appeared to set away quickly and smoothly, allowing the vessel to make tighter turns while towing the net. Tests were conducted off Milbanke Sound to compare a regular light duty semi-balloon Gulf shrimp trawl with chain groundline and towed off the hook on the back edge of the otter boards with the gear that the vessel used (described above). The regular light duty net set away quite adequately when rigged in this fashion and also caught a similar amount of shrimp but the light duty net caught more fish than the net the vessel was using regularly (see Tables - tows 183 to 187). The roller groundline was considered to be effective and it appeared to reduce the numbers of flatfish. On the test fishing the rollers did not seriously reduce the catch rate of shrimp. The roller groundline also appeared to protect the net from extensive damage. On several occasions when the vessel was suddenly stopped while towing because of obstructions, the net was recovered with little or no damage. SURVEY METHODS Before each tow, the area was thoroughly sounded to determine whether the bottom was smooth enough for trawling. Tows were generally 30 minutes long. Special 60-minute tows were made to determine the catch rate of the net on longer tows. Several tows were cut short because of obstructions or snags. All courses given in the Tables are magnetic for the prevailing direction of each tow. A bathythermograph cast to measure bottom tempera ture was taken at the beginning of each tow, and a mud sample obtained at the end of tow from the mud sampler attached to the starboard otter board. When the catch was brought aboard all fish were separated from the catch and weighed. The weights of separate species of fish were estimated. The larger species of shrimp, usually fewer in numbers, were then picked from the catch and weighed. The remaining shrimp, invettebrates, etc., were then weighed, and a random sample of this was taken usually 10-20 lb,, and all the shrimps removed and weighed; from this value the total amount of pink shrimp was calculated. A one-pound sample of each species was then weighed for a count of individuals per pound. - 3 - A sample from the best catch of each particular area or inlet was then sexed and measured (carapace length). Weights of all fish and inver tebrates in each tow were estimated but are not recorded in this report. The actual period of prospecting extended from July 8 to September 6 and 145 tows were attempted. Tables beginning on page 9 describe indivi dual tows, arranged according to areas. Ipf The most important shrimp found was the smooth pink (Pandalus jordani). The pink (Pandalus borealis) was caught in inlets mixed with smooth pink. The second most abundant shrimp caught was the sidestripe (Pandalopsis dispar) which occurred in small quantities on inshore grounds. Other shrimps occurring were prawn (Pandalus platyceros) and negligible amounts of humpback (Pandalus hypsinotus). The positions of tows are shown on the overlays following the Tables. Tow numbers are placed at the end of each tow. Overlays are traced from Canadian Hydrographic charts. Tows which end at a cross signify snags. RESULTS The most promising area found in the 1967 survey was the Pearl Rocks Grounds, a 14 square mile area 5 miles south of Cape Calvert. Twelve tows ^9 were completed in this area within a depth range of 70 to 105 fathoms. Catches yielded between 80 and 630 mixed shrimp made up of 95% smooth pink (134 shrimps to the pound) and 5% sidestripe (33 shrimps to the pound). Another area which yielded excellent catches was the entrance to Quatsino Sound in a small area 2 miles ESE of Kains Island. Previously, this area had been fished fairly successfully in 1954 by the Yuri M in a survey conducted by the Fisheries Research Board in cooperation with the Industrial Development Service of the Department of Fisheries (Circ. No. 35) and in March 1964 by the Fisheries Research Board's vessel the G.B. REED. Two tows (nos. 254 and 255) were completed in depth range of 74-95 fathoms. Catches averaged 335 lb of mixed shrimp, consisting of 877o smooth pink (77 shrimps to the pound) and 13% sidestripe (32 shrimps to the pound). Some good quantities of smooth pink were also caught on the north side of the "Stump Ranch", a commercial trawl area in Queen Charlotte Sound seaward of the Virgin Rocks. Tows 227, 228 and 229 yielded catches of 290, 175 and 240 lb of smooth pink, respectively. The dragging bottom in this area is fairly extensive but some caution is required on the deeper tows. A total of 12,625 shrimps of 4 major species was sexed and measured. Temperature observations and bottom sediments were also collected from every tow, and results may be reported on at a later date. 4 - DISCUSSION Once again it should be emphasized that fishing results are only an indication of shrimps available to a 70-ft Gulf Balloon trawl during the period of study. In other seasons larger or smaller catches cannot be predicted. All that can be predicted however is that the average size of the shrimps reported during the study period will be larger in the fall and winter due to normal growth rate and that smaller counts per pound will prevail. The area off Milbanke Sound was fished extensively this year due to good catches of shrimp in the 1966 survey. (Catches this year were not nearly so large nor so clean). Further exploration in this area during 1967 revealed there is less suitable bottom than previously thought. Laredo Sound yielded some encouraging catches again in 1967. Some caution must be used in this area if commercially exploited. Bottom type indicated on the sounder and revealed by the mud sampler would indicate excellent shrimp ground but there appears to be a scattering of large boulders on the sea bed. Three of the five tows in Laredo Sound contained large boulders in the cod end; fortunately no damage was incurred by the net except for the necessity of dumping one catch overboard as the boulder was too large to land. While catches on the Pearl Rocks Ground were good, another factor 7 must be noted.