July 1966 



COMMERCIAL FISHERIES REVIEW 



39 



of the cruise were used in pelagic fishing and 

 gear evaluation in Puget Sound prior to the 

 scheduled departure date. 



Ky^-'^^iv^ 



Area of operations during M/V John N. Cobb Cruise 77 (April 15- 

 4, 1966). 



OBJECTIVES: The primary objectives of 

 the cruise were to: (1) obtain data on the 

 geographic and bathymetric distribution of 

 northern anchovy during the time interval 

 mid-April-early May; (2) obtain data on the 

 catching efficiency of the modified T-scale, 

 |-inch mesh version of the Mark II 'Cobb" 

 pelagic trawl for northern anchovy; and (3) 

 obtain biological information on northern an- 

 chovy. A secondary objective was to obtain 

 samples of northern anchovy for composition 

 analysis by the Bureau's Seattle Technolog- 

 ical Laboratory. Objectives of the 2 -day 

 pelagic fishing and gear evaluation effort in 

 Puget Sound were to: (1) have SCUBA equip- 

 ped divers assess the degree of structural 

 modification necessary to achieve proper 

 trawl pattern of the |-scale net; (2) fish the 

 unmodified trawl on concentrations of Pacific 

 hake ( Merluccius productus ) in Port Susan; 

 and (3) return samples of Pacific hake and 

 plankton to the Bureau's Seattle Biological 

 Laboratory for biological analysis. 



GEAR: Midwater trawls fished duringthe 

 survey were: (1) the Standard Mark n"Cobb" 

 pelagic trawl, constructed of 3 -inch mesh 

 multifilament webbing, equipped with a full 



2-inch mesh liner in the cod-end, and (2) the 

 modified |-scale, 4-inch-mesh version of the 

 Mark II "Cobb" pelagic trawl. Both trawls 

 were fished with a pair of 5 -by 8 -foot alumi- 

 num hydrofoil-type otter boards attached to 30- 

 fathom bridles. Fishing depth of the trawl 

 was monitored by using a dual electrical depth 

 telemetering system, with the depth sensing 

 units positioned on the trawl at the lower end 

 of the wings. A high-resolution, low-frequen- 

 cy echo sounder was used to locate fish 

 schools. 



METHODS OF OPERATIONS: Onshore- 

 offshore echo-sounding transects were made 

 at oblique angles to the coast between the 10- 

 and 140 -fathom isobaths. Upon location, fish 

 populations were sampled with a pelagic trawl 

 to obtain data on species composition and a- 

 vailability to the trawl. Post-sampling pro- 

 cedures included the outlining of significant 

 schooling areas by closely spaced echo-sound- 

 ing transects. A bathythermograph cast, with 

 its associated sea-surface reference temper- 

 ature, was made after each haul. 



TWO -DAY PUGET SOUND EFFORT: One 

 drag, 2 plankton tows, and 5 bathyihermo- 

 graph casts were made in Puget Sound. A 2- 

 minute drag at latitude 48°06.6' N. and longi- 

 tude 122°22.8' W., was made on strong echo 

 traces ranging between 45 and 63 fathoms over 

 an average bottom depth of 65 fathoms. About 

 9,000 pounds of Pacific hake were collected. 

 A random sample (289 fish) showed a 3.1:1 

 male to female sex ratio, respectively. 

 Length measurements ranged from 31 to 46 

 centimeters (12.2 to 18.1 inches), with males 

 averaging 35.0 centimeters (13.8 inches), and 

 females 37.9 centimeters (about 14.9 inches). 

 Gonads were observed in various stages of 

 development. A brief examination by person- 

 nel from the Seattle Biological Laboratory 

 showed that both plankton samples contained 

 hake-like eggs. Vertical temperature pro- 

 files taken in Port Susan showed surface wa- 

 ter temperatures ranging from 49.8° to 51.2° 

 F., while corrected temperatures at 6 5 fath- 

 oms ranged from 48.5° to 49.9° F. 



SCUBA-eguipped divers observed that the 

 unmodified -f-scale, |-inch mesh version of 

 the Mark II ' Cobb" pelagic trawl showed an 

 excessive amount of ball oning web while un- 

 der tow at a balanced de'ith of 10 fathoms. 

 This feature was successfully corrected by 

 lengthening the criss-cross riblines. This 

 modified version was theii used during the re- 

 mainder of the cruise. 



