16 



COMMERCIAL FISHERIES REVIEW 



Vol. 28, No, 9 



cruise. All drags were made with a 52-foot 

 (headrope) Gulf-of-Mexico-type fish trawl. 

 The majority of drags were of 30 -minutes 

 duration. A total of 5 drags were purposely 

 shortened to 15-minute periods to check for 

 alewife at depths where they were assumed 

 to be absent. The presence of gill nets and 

 rough bottom conditions caused the early ter- 

 mination of 4 other drags. Three short drags 

 were made inside harbor entrance piers and 

 an additional 3 drags were shortened because 

 of snags. Major gear damage occurred dur- 

 ing 2 hauls, one in Port Washington piers, 

 the other at 10 fathoms off Port Washington. 

 Minor gear damage resulted during another 

 drag. The Kaho 's high resolution echo -sound- 

 ing equipment continually monitored and re- 

 corded fish concentrations and bottom con- 

 ditions. 



In conformance with explorations conducted 

 Ln June 1962, difficulty was experienced in 

 catching commercially-significant quantities 

 of alewife with trawl gear. The best concen- 

 trations of alewife were found inside 10 fath- 

 oms where in Lake Michigan the bottom is 

 usually too rough to permit effective bot- 

 tom trawling. Commercially significant 

 quantities of alewife amounting up to 1.8 tons 

 an hour were taken off Benton Harbor, Wau- 

 kegan, Kenosha, Milwaukee, and Port Wash- 

 ington, respectively. The catches, however, 

 were much smaller than those obtained dur- 

 ing earlier cruises in April and May 1966. 



Unusually large catches of 450 and 500 

 pounds of yellow perch were made off Ben- 

 ton Harbor. Little effort was made to locate 

 chubs during this cruise--the largest catch 

 was 120 pounds. 



Among other species caught in the trawl 

 were smelt, sculpin, yellow perch, and lake 

 trout. 



Note: See Commercial Fisheries Review , August 1966 p. 29. 



Great Lakes Fishery Investigations 



BIOLOGICAL RESEARCH AND 



SEA LAMPREY CONTROL, JULY 1966: 



Some of the highlights of Great Lakes bi- 

 ological research during July 1966 by the 

 Biological Laboratory at Ann Arbor, Mich., 

 operated by the Bureau of Commercial Fish- 

 eries, U. S. Department of the Interior: 



Lake Superior research : The Biological 

 Laboratory's research vessel Siscowet op- 

 perated in western Lake Superior during 

 July. Part of the cruise was in support of 

 the University of Minnesota project under 

 P,JL. 88-309 . Assessment of the abundance 

 Euid distribution of lake trout also was carried 

 out at that time. The catch per unit of effort 

 was slightly higher than a year earlier. Two 

 young-of-the-year lake trout were caught 

 during trawling operations in the Apostle Is- 

 lands region of the lake. 



Lake Michigan research : Alewife larvae 

 were abundant during July in the open waters 

 of Lake Michigan off Saugatuck, Mich. They 

 appeared to be confined to the upper few me- 

 ters of water regardless of depth. Although 

 they are found in the lake atvery early stages 

 of development, the pattern of movement 

 would indicate there is little or no actual 

 spawning in the lake off Saugatuck. 



Further study by the Bureau's Biological 

 Laboratory to determine the effect of tem- 

 perature on alewife eggs revealed that hatch- 

 ing may occur over a wide temperature 

 range (52-82° F.). Preliminary field ob- 

 servations indicate that the upper limit for 

 hatching (82° F.) may be the temperature at 

 which natural spawning is completely inhib- 

 ited. All spawning activity in the Kalamazoo 

 River ceased when water temperatures 

 reached 82° F. All mature eggs taken from 

 females inhabiting 82° F. water were dead 

 and sperm from males was highly viscous 

 and would not mix with water. 



Lake Erie research : Assessment of the 

 new year-class strength of various species 

 in the western basin of Lake Erie was con- 

 ducted during July. Results from trawling 

 as of that time indicated the poorest survival 

 of yellow pike and yellow perch in that area 

 since 1957. The research vessel Musky II 

 also was used in supporting the investigations 

 conducted by the Laboratory's iimnological 

 study group off Lorain, Ohio. 



Sea lamprey control: Seasonal operation 

 of electric barriers in Lake Superior trib- 

 utaries was terminated July 13. The adult 

 sea lamprey counts at the assessment bar- 

 riers declined significantly. Catches of 

 spawning-run lampreys showed a 56-percent 

 reduction from the previous 4-year average 

 (10,825). At the end of the season the catch 

 was 4,761 sea lampreys compared with 

 11,834 a year earlier. 



