FISHERY BULLETIN: VOL. 72, NO. 2 

 Table 12. — Four-way analysis of variance of dry weights according to season and sediment type. 



that the rest of Goose Creek, as represented by 

 stations 2-25, also suffered a reduction in biomass 

 from which recovery was not evident 11 mo after 

 dredging. 



Further evidence of the reduction in biomass 

 after dredging can be found in Table 13, which is 

 a comparison of dry weights at stations 2-25 in 

 -June 1967 and 1968, 1 mo before and 11 mo after 

 dredging. Only one station of the 13 (station 11) 

 for which comparative data exist had biomass in 

 excess of the 1967 levels. The significance of any 

 individual datum is not great, since the presence 

 of an adult clam or sea cucumber could inor- 

 dinately affect a particular station. The general 

 trend, however, is clear; 12 out of 13 stations 

 have substantial reductions in biomass. This 

 reduction cannot be attributed to mechanical 

 removal of sediment or specimens, and is attrib- 

 uted to the dredging process itself. 



Chi-Square Analysis of Number of 

 Species and Specimens 



Chi-square analyses were performed to deter- 

 mine whether or not the number of species and 

 individuals in the post-dredging series differed 

 significantly from the pre-dredging population. 

 Data were further analyzed to determine if sub- 

 stratum and seasonal variations affected species 

 diversity and numbers of individuals. Table 14 

 represents the chi-square analysis of the number 

 of species before and after dredging for the whole 

 bay (minus the intertidal stations), the bay sta- 

 tions plus the channel stations, and the channel 

 stations alone. In all cases the chi-square was 

 significant, indicating that species number was 

 affected by dredging. Since chi-square analysis is 

 limited by its inability to discriminate between 

 sign (-1- or -), Table 15 tabulates the number of 

 species found at stations 2-25 in June 1967, 1 mo 

 before dredging, and in June 1968. A reduction in 



species number occurred at 75% of the stations 

 after dredging, with three stations or 18.7% 

 exhibiting small increases in species number. 



A chi-square analysis was performed on the 

 number of species according to sediment type 

 (e.g., sand, muddy sand, mud-silt). The number of 

 species altered significantly according to sub- 

 stratum after dredging, both in the bay as a whole 

 and in the channel (see Table 16). 



Table 13. — A comparison of dry weights from stations 2-25, 

 June 1967 and June 1968 (in g). 



Station 



2 



3 



4 



5 



6 



7 



3 



9 



9A 

 10 

 11 

 12 

 13 

 14 

 15 

 16 

 17 

 18 

 20 

 21 

 22 

 23 

 24 

 25 



June 1968 



9,47 



16,13 



00 



0.92 

 0,31 



1.04 



0.15 

 83 



0,07 

 1,64 

 1.82 



000 

 0,71 

 0.41 

 1.08 



0,01 

 0,005 



Table 14.— Chi-square analyses of the number of species before 

 and after dredging for stations 2-12, 14-19, 22, 23; stations 

 2-12, 14-19, 22, 23 plus channel stations A-J, M, and stations 

 A-J, M alone. 



462 



