Figure 13.— Total vessel days fished, total vessel days 

 fish landed, and total standard vessel days in Chesa- 

 peake Bay, 1964-67. 



Figure 14.— Total vessel days fished, total vessel days 

 fish landed, and total standard vessel days, Southport 

 N.C., 1963-67. 



Totol Vessel Days Fished 



\ 



Total Stondord Vessel Days 

 Tofol Vessel Days Fish Londed 



Figure 15.— Total vessel days fished, total vessel days 

 fish landed, and total standard vessel days at Wild- 

 wood, N.J., 1964-67. 



total standard days are shown in Figures 14 

 and 15. Data from one company for North 

 CaroUna are shown in Figure 14. All three 



curves fluctuate in a somewhat similar manner. 

 The percentage of unsuccessful fishing days 

 varied from around 35 to 45%. For certain 

 boats at Wildwood, N.J., for which data were 

 available (Fig. 15), the number of days fished 

 without catching anything increased markedly 

 in 1966 and 1967, causing the increased 

 discrepancy between the curves for total vessel 

 days fished and the total vessel days fish 

 landed. This increased difference obviously 

 reflects the poorer fishing on the reduced 

 stocks of fish in recent years. The curve for 

 total standard vessel days closely follows that 

 for total vessel days fish landed. It appears that 

 total days fished might be a better measure of 

 fishing effort. Unfortunately, these data are 

 not available from most companies and would 

 have to be estimated from log book data. Such 

 a course certainly should be considered in 

 future analyses. 



In an attempt to avoid the problem of 

 recording no effort for days when fishing effort 

 was expended but no fish were caught, as well 

 as to reduce the amount of work required to 

 compute fishing effort, a vessel-week unit of 

 effort was developed. Under this procedure if a 

 vessel fished anytime during a week it was 

 considered as fishing for that week. Thus, a 

 vessel that fished only 1, 2, or 3 days would be 

 given as much weight as a vessel that fished 5 

 or 6 days of the week. This might be most 

 important in the North Carolina fall fishery 

 where the weather greatly affects the number 

 of days fished. The vessel week unit of effort 

 tends to reduce the accuracy of the estimated 

 number of units of effort aiid the amount of 

 data available as well as to reduce the differ- 

 ences between years. For the period 1955 

 through 1968 on Chesapeake Bay, there were 

 only about 257f as many vessel weeks as 

 standard vessel days. There is no evidence that 

 the vessel week is any better or any worse a 

 measure of fishing effort than the standard 

 vessel landing day. In fact, there is a rather 

 constant relation between the catch per vessel 

 week and the catch per standard vessel day, as 

 demonstrated by data for the Chesapeake Bay 

 fishery in Figure 16. Furthermore, there is a 

 very close correlation between the number of 

 vessel weeks and the number of standard vessel 

 days. For the 1955 through 1968 data, from 

 Chesapeake Bay, these two units of effort had 



