FISHERIES EST MICHIGAN WATERS OF GREEN BAY 



33 



fyke nets, the other two gears employed in the esti- 

 mation of abundance. 19 Much of the relatively 

 greater success of the trap nets, it was explained, 

 probably resulted from the introduction of larger 

 nets capable of taking more walleyes per lift at 

 a given population level than were taken by the 

 gear formerly employed. Any increases in the 

 catch per net that resulted from change of gear 

 rather than from increased abundance, of course, 

 contributed to an overestimate of the index of 

 abundance and an underestimate of the index of 

 fishing intensity. 



The discrepancies between the data for trap nets 

 and those for pound nets and fyke nets that were 

 troublesome in the 1947-49 statistics became exces- 

 sive in 1950, as is seen from the following tabu- 

 lation : 



1950 catch as 

 Catch per lift (pounds) percentage of 

 1929-43 1950 average 



Pound nets 19 21 111 



Shallow trap nets 8 74 925 



Fyke nets 32 50 175 



Although the discrepancies indicated above are so 

 large as to make the computation of general indices 

 of abundance and fishing intensity undesirable, the 

 original data do provide some useful information. 

 There can be little doubt, for example, that in 1950 

 the abundance of walleyes continued to be sub- 

 stantially above the 1929-43 average. The lowest 

 estimate for a single gear was 111 percent (pound 

 nets) and the other gear for which we have no 

 reason to suspect biased records (fyke nets) 

 yielded the higher figure of 175. Furthermore, we 

 cannot overlook the possibility that the high figure 

 for trap nets resulted from a heavy concentration 

 of walleyes on the trap-net grounds as well as from 

 the introduction of more efficient nets. Hence, on 

 those fishing grounds the relative abundance may 

 have been in fact at a level higher than that indi- 

 cated by the data for either pound nets or fyke 

 nets. 



The continued high (if not precisely measured) 

 abundance and the enormous yield of walleyes in 



10 Data from large-mesh gill nets, a major gear In the production 

 of walleyes In 1947-50, cannot be used for the estimation of 

 abundance since we have been unable to establish a long-term 

 normal catch per lift. In 1929-46, the production of walleyes 

 by this gear was too small to yield dependable data on the take 

 per unit effort. Tiie annual take averaged only 1,940 pounds over 

 that period, and In 7 of the 18 years the catch was less than 1,000 

 pounds. 



1950 are a tribute to the phenomenal strength of 

 the 1943 year class. That group, according to 

 Robert F. Balch, 20 strongly dominated the com- 

 mercial catch in State of Michigan waters of Green 

 Bay in 1950; furthermore, an early 1951 sample 

 indicated that walleyes hatched in 1943 would 

 form the main support of the 1951 fishing. 



Yellow perch : The year 1950 saw an end to the 

 downward trend that had carried the index of 

 abundance from a high of 150 in 1945 to 49 in 1949. 

 The improvement to 52 in 1950 was, of course, 

 small, but it does lend hope that a recovery of the 

 stocks may be under way. The increase in the 

 catch of yellow perch from 65,000 pounds (37 per- 

 cent of the 1929-43 average) in 1949 to 107,000 

 pounds (Gl percent) in 1950 came principally from 

 the upswing in fishing intensity from an index 

 value of 77 in the former year to one of 119 in the 

 latter. 



White and redhorse suckers: With the suckers 

 as with the yellow perch a slight rise in the abun- 

 dance index (from 61 in 1949 to 03 in 1950) gives 

 us hope that a period of low availability may be 

 nearing its end. Despite the small improvement 

 in abundance the production of suckers fell from 

 878,000 pounds (120 percent of the 15-year nor- 

 mal) in 1949 to 729,000 pounds (99 percent) in 

 1950. The decline can be traced to a drop in fish- 

 ing intensity from 194 to 155. 



Smelt : The recovery of production following 

 the mortality of 1943 continued in 1950 when the 

 catch of 1,024,000 pounds (222 percent of the 1929- 

 43 mean ) was 574,000 pounds greater than the 1949 

 yield of 1,050,000 pounds (144 percent). Com- 

 parisons of the catch per lift in 1950 (table 24) 

 with (hose of 19-19 (table 17) prove that the in- 

 crease in the take resulted from an upswing in 

 fishing pressure. With the exception of the equal 

 catches of 28 pounds per 1,000 feet of bait nets in 

 January of both years, the production per unit of 

 fishing effort was consistently higher in 1949 than 

 in the same month and with the same gear in 1950. 



Total production : The take of 8,578,000 pounds 

 (282 percent of the 1929 — 13 average) constituted 

 a new high in the modern period which began with 

 1929. The principal contributors to the rise from 

 7,782,000 pounds (256 percent) in the previous 

 year were lake herring, smelt, and walleyes with 



"Unpublished manuscript submitted to the Wisconsin Conser- 

 vation Department. 



