Borgeson 1965). Since the catches did not differ 

 significantly, all beaches were treated together for 

 predictive purposes. An estimate of the total crabs 

 caught by intertidal sport crabbers for the day- 

 light tides in 1974 was made by multiplying the 

 average catch per effort for April, May , June, July, 

 and August at Mission Beach (Table 4) by the 

 estimated total number of crabbers (Table 3) for 

 each month. The number of crabs caught per 

 month increased throughout the spring, reaching 

 a maximum of 5,099 in June. Few crabs were 

 caught after July (Table 5). 



When Spearman rank correlation coefficients 

 were computed between a crabber's catch at Mis- 

 sion Beach and a number of independent variables 

 (Hollander and Wolfe 1973), the most significant 

 positive correlation was with the total time spent 

 crabbing (Table 6). Crabbing was better in April- 

 June than in July and August. The tide height and 

 tide sequence were not significantly correlated 

 with the catch per crabber at P<0.05, but were 

 significant at P<0.10. The highest average 

 catches were on tides ranging from -0.60 to -0.74 

 m (Table 2). 



The higher tides make crabbing difficult, be- 

 cause crabbers have to wade into deeper water to 

 get to the area where crabs are found. In the 

 deeper water, crabs are less visible and the mobil- 

 ity of crabbers is impaired. The catches and 

 number of crabbers arranged by tide sequence are 

 shown in Table 7. The lowest tides of the year are 

 generally four or five tides into a tidal series. The 

 first low tides in the series have already allowed a 

 fair amount of crabbing pressure on the beach, and 

 many of the available crabs have been removed. 

 Additionally, the combination of crabbers wading 

 and less water over the beach on the previous low 

 tides probably causes crabs to move to deeper 

 water during the last low tides in a series. 



The sex and size composition of crabs that I 

 observed while sampling are shown iti Figure 3. 

 The numbers of legal males (152 mm and larger) 

 include all crabs measured during crabber inter- 



TaBLE 4. — Monthly crabber use and mean daily catch at Mission 

 Beach, Wash., Apnl-August 1974. 



Mean daily Range of 

 Number of Number of catch per mean daily 

 Montti tides crabbers crabber catches 



Table 5.— Estimated total Dungeness crab sport catch in Puget 

 Sound on intertidal beaches. April-August 1974. 



Table 6. — Spearman correlation coefficients between number 

 of crabs caught per crabber and nine independent variables. 



Variable 



Time spent crabbing 

 Month 

 Tide height 

 Tide sequence 

 Wind velocity 

 Temperature 

 Precipitation 

 Time of low 

 Cloud cover 



Significance 



0001 

 002 

 .055 

 .061 

 .113 

 .238 

 .263 

 355 

 473 



Table 7. — Crabber use and catch taken on different tide heights 

 arranged according to the sequence in which they occurred in a 

 low tide series at Mission Beach. Wash., April-August 1974. 



2251 



100 



75- 



50^ 



25- 



MAIESQ 

 FEUIAIESQ 



JL 



<108 114 121 12; 133 140 146 152 159 165 171 178 184 < 

 LENGIH mm) 



Figure 3, — Size composition and sex of crabs observed during 

 sample crabbing at Mission Beach from October 1973 through 

 August 1974, Male crabs -">150 mm include those measured 

 during crabber interviews. 



291 



