240 



FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE 



perch in the gill-net collections does not represent 

 gUling but, as stated earlier, is the result of the 

 entanglement of the marginal bones of the mouth 

 or of the fins in the gill-net webbing. 



The occurrence of illegal-sized yellow perch in 

 unpounding-net samples (table 17) varied from a 

 maximum of 78.8 percent in 1928 when the 

 collections were dominated by the 1926 year class 

 as age group II to a minimum of 38.1 percent in 

 1929 when the same year class was dominant as 

 age group III. Had the computation for 1928 

 been made on the basis of the then-effective size 

 limit of 9 inches instead of the current 8% inches, 

 the proportion of undersized yellow perch would 

 have been even greater — 89.6 percent. The 1927 

 collection which was dominated by the 1926 year 

 class as age group I nevertheless had relatively 

 fewer illegal-sized yellow perch (61.1 percent 

 computed from a size limit of 8% inches and 76.2 

 percent from a size limit of 9 inches) than the 1928 

 collection. An explanation of this discrepancy 

 was given on page 237. Perch under the legal size 

 limit were in the minority in the impounding-net 

 samples in only 2 of 7 years (1929 and 1932). 

 The percentage of undersized perch in the collec- 

 tions of all years combined, computed from a size 

 limit of 8% inches, was 55.6. 



Illegal-sized yellow perch were relatively much 

 less abundant in the gill-net than in the impound- 

 ing-net catches, except in the 1927 bull-net 

 samples which contained a high proportion of 

 small, accidentally captured fish. Undersized 

 individuals in shoal-net samples varied from a 

 maximum of 15.9 percent in 1927 to a minimum 

 of 2 percent in 1929 and amounted to 6.2 percent 

 for the 3 years' collections combined. Com- 

 puted from the then-effective size limit of 9 inches, 

 the 1927 and 1928 percentages would have been 

 higher — 20.3 and 23.4. The percentages of under- 

 sized yellow perch in bull nets were 54.9 in 1927, 

 17.0 in 1928, and 1.4 in 1929. On the basis of the 

 then-effective size limit of 9 inches these would 

 have been increased to 59.1 and 33.2 percent in 

 1927 and 1928. For all years combined the per- 

 centage of illegal-sized yellow perch in the bull 

 nets was 15.1 as compared with 6.2 in the shoal- 

 net collections. The percentage of Ulegal-sized 

 fish in all gill nets was 7.6. 



The proportion of illegal-sized yellow perch in 

 gill-net catches provides a fairly precise measure 

 of the destruction of undersized individuals by 



this type of gear, as practically all individuals are 

 dead at capture or are killed in the process of 

 removal from the nets. It should be noted, 

 however, that on the average the percentage of 

 undersized fish in gill-net samples usually fell well 

 below Ohio's legal allowance of 10 percent in the 

 conomercial catch, especially since the allowance 

 is based on weight rather than on numbers of fish. 



The destruction of illegal-sized yellow perch can 

 be determined less accurately for impounding nets 

 than for gUl nets because the trap-net and pound- 

 net fishermen are required to return all illegal- 

 sized fish to the water. It is relatively certain 

 that an unknown portion of these fish die as the 

 residt of handling. It is known that on the aver- 

 age 14 percent of the Ulegal-sized perch taken by 

 Lake Erie trap nets are dead at the time of lifting. 

 (See footnote 5, p. 221.) Since 55.6 percent of the 

 yellow perch from impounding nets were under- 

 sized, it may be computed that for every 1,000 

 yellow perch taken, 76 illegal-sized fish were de- 

 stroyed. This value was well below the 151 de- 

 termined for buU nets but was above the 62 for 

 shoal nets, and equaled the 76 from all gUl nets. 

 However, the computed number of illegal-sized 

 yellow perch destroyed by impounding nets must 

 be considered as the minimum since it does not 

 include those fish that are lolled during the sorting 

 of the catch to conform to the legal-size limit. 

 Further, impounding nets took many more fish 

 during the year than did the gill nets and therefore 

 destroyed many more individuals. The data seem 

 to offer good support to Van Oosten's (1936) con- 

 clusion that more fish are destroyed by trap nets 

 than by gUl nets. 



The importance of the destruction of small 

 yellow perch by trap nets is emphasized when it is 

 remembered that in recent years this gear has 

 accounted for approximately 61 percent of all 

 perch taken in the United States waters of Lake 

 Erie (65 percent of those taken in Ohio waters) .^^ 



Table 18 contains a summary of the length fre- 

 quencies (total lengths) by half-inch intervals, the 

 percentage frequencies, and the cumulative per- 

 centages for Lake Erie yellow perch taken in 

 different types of gear, with all years' collections 

 combined. Practical considerations make such 



13 Percentages were computed from data for the calendar years 1930, 1931, 

 1932, 1934, 1936, 1937, and 1938 contained in the former V. S. Bureau of Fish- 

 eries publication, "Fisheries Industries of the United States," Report of the 

 Commissioner of Fisheries, for 1931, 1932, 1933, 1935, 1937, 1938, and 1939. 



