FISHERY BULLETIN: VOL. 76, NO. 2 



Efford (1967:84, figure 3) presented a growth 

 curve forE. analoga, constructed from data taken 

 from 22 beaches on the Pacific coast between En- 

 senada, Mexico, and Tofino, Canada (a 2,400 km 

 distance). Three-fourths of the data presented 

 were gathered over a period of only 2 mo (between 

 17 June and 17 August 1961). The remaining data 

 were collected in 1959 and 1963. Where size- 

 frequency data were bimodal, the author assumed 

 that two year classes were present. To construct a 

 growth curve from his data, Efford also had to 

 assume that: 1) growth rate was the same year to 

 year (temporally stable, at least during the grow- 

 ing season); and 2) longshore migration did not 

 take place for E. analoga. 



Dillery and Knapp (1970) demonstrated that an 

 average E. analoga individual of about 26 mm 

 carapace length travels about 15 m/day 

 alongshore in an easterly direction on local 

 beaches in Santa Barbara. This implies that the 

 individuals in inhabiting a particular location 

 may change from day to day. Barnes and Wenner 

 (1968) suggested that the interpretation of size- 

 frequency data is considerably simplified if sex 

 reversal is assumed for this species, and some di- 

 rect evidence (Wenner 1972) supports this as- 

 sumption. However, recent laboratory data (Fu- 

 saro 1977) suggest that a differential growth rate 

 for males and females between 9 and 14 mm 

 carapace length may account for the observed 

 size-frequency distributions and sex ratio pat- 

 terns, rather than protrandry. 



Combining data from different beaches, as Ef- 

 ford ( 1967) did, also carries with it the assumption 

 that the growth rate is relatively the same for the 

 various parts of the range o^E. analoga (spatially 

 stable). However, in an analysis of E. talpoida 

 data presented by Wharton (1942), Efford 

 suggested that the growth pattern of this latter 

 species may differ in the southern part of its range. 

 It is likely that temperature was responsible for 

 the difference, as it is likely that temperature has 

 an effect on the growth of £. analoga in different 

 parts of its Pacific coast range. 



Wenner et al. ( 1974) presented data (their figure 

 5) which suggested that for E. analoga, even dif- 

 ferent local populations may display different 

 growth patterns, at least as indicated by size at 

 sexual maturity. Data presented in this report 

 imply that molt increment and molt frequency are 

 indeed different in different environmental re- 

 gimes in nature. Growth curves constructed for 

 such different areas would likely differ. To com- 



bine these sets of data would be to obscure the real 

 differences in growth rate observable in such local, 

 proximate populations. 



The instantaneous growth rate estimate, 

 though, may be used as an index of how well a 

 population fares under a given set of environmen- 

 tal conditions. Consider this instance. It has been 

 shown that a population oiE. analoga on a beach 

 at Santa Cruz Island grew about one-third as fast 

 as a population in Groleta Bay (molt increment 

 depressed by one-third and molt frequency de- 

 pressed by one-half). Assuming a fixed number of 

 molts to maturity (e.g., Wenner et al. 1974, table 

 1), the island population would reach maturity at 

 a smaller size and in about twice as long a time. In 

 fact, population structure data (Table 3) shows 

 that sand crabs from the island population 

 reached maturity at about the same size as those 

 from Goleta Bay. If a fixed size at maturity is 

 assumed, the island population sampled would 

 take about three times as long to reach that fixed 

 size. 



The third possible assumption, that there is a 

 fixed length of time to maturity, is argued against 

 by all available data. In any of these cases, how- 

 ever, the population of sand crabs inhabiting the 

 beach of the Santa Cruz Island bay location was at 

 a distinct disadvantage in terms of reproductive 

 success when compared with the population oiE. 

 analoga inhabiting the Goleta Bay beach. This 

 reproductive disadvantage was brought about at 

 least in part by the large observed differences in 

 molt frequency and molt increment at the two 

 locations. A much smaller percentage of females 

 were of reproductive size, probably due to the dif- 

 ferential growth rate (see Table 3). 



Cox and Dudley ( 1968) also reported large vari- 

 ations in the size of the smallest egg bearing 

 female £^. analoga found in their collections. Data 

 presented here may account for such previously 

 problematical observations, in that differences in 

 growth rate may affect the size distribution and 

 abundance of mature females. 



As these data suggest, then, the growth rate of a 

 crustacean population plays an important role in 

 the life history of that species in its particular 

 environmental situation. Of course, when dealing 

 with a species which has pelagic larval stages, it 

 becomes difficult to study local populations under 

 the assumption that they are genetically different. 

 Recruitment patterns are not generally well 

 known for species with pelagic larvae (see Thorson 

 1950; Efford 1970; Mileikovsky 1971; Strathmann 



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