8-41 



during the seven-year program, 14 were encountered every year of the 

 study (1971-1977) . An additional six were encountered during all of the 

 last five years (1973-1977). Thus, of the 24 to 28 invertebrate taxa 

 collected annually bo^qinning in 1973, 20 taxa or 70 to B0'(, of tlio.sc; 

 collected each year were common to all years. The remaining 20 to 30%, 

 4 to 8 species, that were not collected consistently were made up of 

 species which: 1) are not commonly collected in otter trawls (Crepiduia 

 convexa, Haminoea solitaria and Retusa obtusa) , 2) generally occur in 

 low abundances in the areas sampled {Eupleura caudata, Palaemonetes 

 vulgaris; and 3) are near their northern geographic limit and occur 

 occasionally in the harbor {Libinia dubia, Penaeus aztecus) . 



Variations in annual abundance of the 12 most commonly col- 

 lected invertebrate species during preoperational and operational years 

 generally fall into four main categories (Table 8-3) : 1) small with no 

 substantial difference between years — i.e., Pagurus longicarpus , 

 Homarus americanus , and Neopanopi sayi; 2) fluctuating, with periods of 

 high and low abundances observed during both preoperational and oper- 

 ational years -- i.e., Ovalipes ocellatus , Cancer irroratus , Ilyanassa 

 obsoletus , Nassarius trivitatus , and Crangon septemspinosa; 3) trends of 

 increasing abundance — i.e., Squilla empusa and Pagurus pollicaris , and 

 4) trends of decreasing abundance — i.e., Asterias forbesi and Libinia 

 emarginata. Species included in the first two categories pose no par- 

 ticular concern since their abundances appeared stable over the period 

 of this monitoring study. Abundance trends of species included in the 

 last two categories warrant further consideration and explanation since 

 long-term changes could conceivably be indicative of Harbor Station 

 impact. 



The hermit crab, Pagurus pollicaris , which belongs to the 

 third category, is typically collected most abundantly in the outer 

 harbor (Stations 19 and 20) . Abundance in sampling hauls has increased 

 from a yearly total of 9 in 1974 to 185 in 1977. Because of its restricted 

 distribution to the outer harbor, however, it is doubtful that the 

 Harbor Station discharge has any relationship to the increasing abun- 



