Environmental Analysis Tools - Environmental Impact Analysis: Process and Methods - page 293

degree on the benthic infauna and epibenthos as food, and the effects of lost
or altered benthic habitat on food availability were calculated to determine
whether the measurement endpoints would be met.
A process was followed relating the loss of benthic fauna to the nutritional
needs of the other endpoint species through evaluation of diet and abun-
dance of food (Figure 7.8). The diet of each endpoint representative species
was determined by a combination of literature review and examination
of gut contents of collected specimens. The predicted effect on the diet of
each endpoint was determined as the combination of percentage of diet of
prey item and loss of that prey item density due to habitat loss or alteration
(Figure 7.9). For example if 10% of a halibut's diet was tanner crab and the
predicted decline in tanner crab density caused by the tailings discharge
was 1.0%, there would be a 0.1% (1% × 10%) reduction in the halibut's avail-
able food supply. This was then summed over all dietary items to determine
the projected food loss for each ecological endpoint species (Table 7.7).
The risk estimates for all endpoints were deemed by the project team, reg-
ulators, and TAC to be within an acceptable range. The loss of food, which
was the only area of potentially elevated risk was deemed within natural
variability and not of concern for almost all of the representative species,
thus the endpoints were achieved. The projected 2.6% reduction in the seal
diet was of some concern (Table 7.7). However, when the conservative nature
of all of the calculations and assumptions, the diversity of the seal diet, and

Food source
location

Area
affected

Portion of
diet affected

Determine
food source

Food source
density

FIGURE 7.8
Food loss prediction process.

TABLE 7.7
Representative Species Food Loss from AJ Mine Tailings Discharge

Percentage of
Diet Loss (%) Representative Species Food Items Affected

Herring Meroplankton 0.6

Salmon Pelagic fish, 0.4

Murre Pollock 1.1

Seal Pelagic fish, sole, squid, octopus 2.6