PERIOD ABOUT LOW TIDE iMINUTES) 



Figure 2. — Crabber use curves for Mission Beach based on data 

 gathered April-August 1974. 



April and August, but I was able to construct use 

 curves for May -June and July, a combined total for 

 those beaches based on 10 and 5 observations, 

 respectively. These use curves, when superim- 

 posed over the corresponding Mission Beach use 

 curves, did not vary by more than approximately 

 10% for the period before, or 20^f for the period 

 after, the low tide. 



The Washington Department of Fisheries also 

 provided me with data from aerial surveys con- 

 ducted over Puget Sound beaches on 27 April, 25 

 May, 22 June, and 20 July 1974. Most of the 

 beaches were surveyed during the hour preceding 

 the low tide, which corresponded to the highest 

 beach use. Thus, the curves derived for Mission 

 Beach were used for estimates for all beaches. 



While interviewing crabbers at Mission Beach, 

 it appeared to me that both the tidal height and 

 tidal sequence were important factors in crabbing 

 success. I therefore analyzed the data in two dif- 

 ferent ways. The various tidal series had from 

 three to eight tides lower than -0.15 m(-0.5ft). I 

 divided the low tide heights into six levels by 

 0.15-m increments. The first minus tide of a series 

 to fall into a tidal height category was defined as 

 Tide One in the tidal sequence. Each succeeding 

 tide was consecutively numbered, with the final 

 tide in a series designated as the last minus tide to 

 fall into a tidal height category. Thus, low tides of 

 equal height from different tidal series were not 

 always the same sequence number. 



Results and Discussion 

 The number of crabbers using Mission Beach 



during the winter nighttime tides was small com- 

 pared with the number during the summer day- 

 time tides. Of the estimated 762 crabbers using 

 Mission Beach during the year, only 27 (4'7f) 

 crabbed from October through February, while 

 735 (96% ) crabbed from April through August. Of 

 the estimated 531 crabs taken for the year at Mis- 

 sion Beach, the winter crabbers caught 60 (11%), 

 while the summer crabbers caught 471 (89%). 



Stepwise multiple linear regression analysis 

 (Poole 1974) of crabber activity at Mission Beach 

 correlated significantly (P<0.05) with tide height, 

 day of week, month, temperature, and wind veloc- 

 ity (Table 1 ). However, the resultant equation was 

 not strong enough for predictive purposes. The 

 tide height accounted for the largest amount of the 

 variability. The lowest three tide levels had two to 

 four times as many crabbers as the highest three 

 levels (Table 2). The other significant variables 

 indicated the following: weekend use by crabbers 

 per tide was 1.5 times greater than the average 

 weekday use per tide; the average number of crab- 

 bers per tide was highest in April, May, and June, 

 with the use dropping off considerably in July and 

 August; there were more crabbers at higher air 



Table L— Summary table of multiple linear regression be- 

 tween total crabbers at Mission Beach and nine independent 

 variables. The resultant equation was significant at P<0.001 for 

 all steps. 



^The Q level of significance for each variable as it was entered in the equation 



Table 2. — Crabber use and catch taken on six different tide 

 heights (mean lower low water) at Mission Beach, Wash., 

 Apnl-August 1974. 



-0 15 to 



-0 29 

 - 30 to 



-0 44 

 -0 45 10 



-0 59 

 -0 60 to 



-0 74 

 -0 75 to 



-0 89 

 -0 90 to 



-1 04 



6 

 14 

 16 



6 



13 

 9 



25 

 27 



1 4 

 79 

 6 1 

 24 7 

 150 

 54 



02 

 06 

 07 

 1 3 

 06 

 02 



7 



110 



92 



173 



62 



27 



289 



