666 



Fishery Bulletin 100(4) 



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 CD 



Test diameter (mm) 



Figure 4 



Size distribution of red sea urchins harvested 

 from the three selective harvest sites com- 

 bined in San Juan Channel (SJC) in March 

 1997 (fi = 1194) and March 1998 l/!=387). 

 Dashed lines indicate minimum and maxi- 

 mum size limits for commercial harvest in 

 SJC. 



Fig. 4). The harvest consisted of 0.5% (±0.4%) under*-size 

 sea urchins, 59.5% (±6.6%) legal*-size sea urchins, and 

 39.9% (±9.2%) over*-size sea urchins. Sea urchins har- 

 vested in the second annual size-selective hai^vest in 1998 

 were 100-155 mm in diameter (mode 130 mm). The com- 

 position of the harvest was similar: 0.0% (±0.0%), 57.1% 

 (±18.7% ), and 42.9%' (±18.7%) of sea urchins were under*-, 

 legal*-, and over*-size, respectively. 



The initial size-selective harvest did not significantly al- 

 ter the size distribution of the population (P=0.18, Fig. 5) 

 but did significantly reduce the density of legal*-size sea 

 urchins (P=0. 05, Table 2). The cumulative effect of two an- 

 nual size-selective harvests on the size distribution of the 

 population was highly significant (P<0.0001, Fig. 5) and 

 significantly reduced the density of legal*-size sea urchins 

 (P=0.03, Table 2). The modal size of sea urchins in selec- 

 tive harvest sites increased to 150 mm after the second an- 

 nual harvest (Fig. 5). Six months after the second annual 

 harvest, the size distribution of the population remained 

 significantly different from the original (1997 preharvest) 

 size distribution (P=0.0001). Size distributions of sea 

 urchins in selective harvest sites did not differ between 

 fall 1997 and fall 1998 according to large-scale sampling 



45 

 40 

 35 

 30 

 25 

 20 

 15 

 10 

 5 

 



Complete tiarvest 



> < -t* » 



" Selective harvest 



E 



Z 



"I^O n Control 

 120 



Test diameter (mm) 



Figure 5 



Size distribution of red sea urchins in the complete 

 han'est, selective harvest, and control treatments 

 in San Juan Channel (SJC) in early March (before 

 harvest), mid-March ifive days after harvest), and 

 September (180 days after harvest) of 1997 and 

 1998. Solid lines represent sampling periods in 

 1997, and dashed lines represent sampling peri- 

 ods in 1998. Cumulative sample sizes for the three 

 sites within each treatment and for all sampling 

 periods illustrated are n = 149, 518, and 1627 

 for the complete harvest, selective harvest, and 

 control treatments, respectively. Samples are from 

 urchins measured in situ in sampling circles. One 

 site (mid SJIl was excluded from the 1997 early 

 March sampling period for the complete harvest 

 treatment. 



(P=0.06), averaging 5.8%, 34.3%-, and 60.0% for under*-, 

 legal*-, and over*-size sea urchins, respectively (:7=756). 

 Size distributions of sea urchins in control sites, based on 

 small-scale sampling, were similar throughout the study 

 (Fig. 5) and did not differ between fall 1997 and fall 1998 

 according to large-scale sampling (P=0.10). 



