392 U- S. BUREAU OF FISHEIIIES 



serves to increase tlie drain on the fishery to nearly the same extent 

 as the capture of equal numbers of marketable haddock. In other 

 words, this destruction in some years doubles and trebles the strain 

 on the fish population, and on the average must form a very consider- 

 able part of the fishing mortality. There also has been an increasing 

 trend toward the marketing of smaller haddock, many averaging 

 little more than half a pound in weight. Given another year on 

 Georges Bank, these fish would treble in weight while in 2 years they 

 would weigh nearly five times as much and be of more value per 

 pound. 



Recommendations. — There appear to be four possible measures 

 that would decrease the destruction of undersized haddock. These 

 are closed seasons, closed areas, minimum market size, and minimum 

 mesh size. Of these, the most effective and practical are a minimum 

 mesh size and a minimum market size. In 1931 and 1932 a practical 

 type of "savings gear" for the New England otter-trawl fishery was 

 develoi>ed through an extensive series of experiments. A report 

 on this work was published in 1935 recommending a minimum 

 mesh size of 4% inches for use in all otter trawls. So far, little 

 action has resulted from this recommendation in spite of the clear 

 evidence in its favor. 



A more popular description of the savings-gear work and of the 

 importance of saving undersized fish, is in preparation for use as 

 a fisheries circular. It is hoped that this will find a wider audience 

 because of its less technical nature. Certainly, convincing the 

 trawler operators and fishermen of the importance of protecting 

 small fish is a prelude to any effective action. 



Savings gear experiments have demonstrated a practical method 

 by which the strain on a fish population can be decreased without 

 the application of any restriction such as closed seasons or closed 

 areas. Adjustment of mesh size to reduce the destruction of small 

 ^^nmarketable haddock certainly will reduce the strain without curb- 

 ing the fishery. Furthermore, in cases where over-exploitation is 

 reducing a fish population to uneconomic levels of abundance, adop- 

 tion by the operators of a suitable mesh size should prove more effec- 

 tive in conserving the fishery than restrictions such as closed seasons 

 or closed areas. Once growth rates and natural mortality rates have 

 been established, it appears possible to determine the average fish 

 size that will produce a maximum catch over a period of years with- 

 out depleting the population. Then, by proper adjustment of the 

 selective gear (mesh size in the case of the otter-trawl fishery), it 

 should be possible to eliminate from the commercial catch a large 

 proportion of the young, rapidly growing fish below this size. If 

 this permits the survival of an adequate spawning stock, it may 

 well be that such protection would be sufficient to prevent real deple- 

 tion, irrespective of the intensity of the fishery. In the case of the 

 North Atlantic haddock, we do not yet have such data as will permit 

 the determination of this optimum size, but there is some indication 

 that on the Nova Scotia banks it may be not fai* from the present 

 accepted minimum commercial size. 



MACKEREL 



With the resumption of unrestricted fishing in 1935 the offshore 

 fleet landed 53,000,000 pounds of mackerel, the largest catch of the 



