Impacts of Seafood Waste Discharge in Orca Inlet, Prince William Sound.

摘要

In 1975 EPA produced effluent discharge guidelines for the seafood processor industry that required wastes to be ground to less than 1.27 cm prior to discharge. Subsequently, several negative impacts were observed around Cordova, including noticeable decreases in crab and halibut harvests and a substantial increase in numbers of gulls. We hypothesized that the change removed a food source for the large bottom-oriented animals and increased availability to the surface-oriented gulls. In 2004, we began a three year study to examine impacts of seafood waste discharge into Orca Inlet, including evaluation of alternative discharge and disposal methods. The study included model development and control-treatment experiments. We developed a dispersal model that incorporated both physical and biological transport mechanisms and demonstrated improvements over current practices. We dumped over 325,000 lbs of salmon heads and carcasses at an experimental site and monitored the biotic response. Methodologies included underwater cameras, traps, acoustic tags attached to salmon heads and visual surveys of birds and marine mammals. The results show that the heads and carcasses disperse rapidly and are efficiently incorporated into the food chain with no negative consequences, a very favorable contrast to the current EPA-mandated practice. The model also revealed that the historic practice of dumping fish carcasses was a far more effective recycling mechanism. In fact fish production may have been substantially reduced with the change in disposal practices since natural recycling is hindered by the discharge of ground waste. We conclude that it is overdue for some rethinking of fish waste practices. The policy of grinding fish waste to the same 1/2 inch grind size that was historically used for sewage wastes in the 1970's needs to change. We need to better understand natural recycling with regard to disposal practices. Fish processing waste is potentially a healthy source of food for marine fauna. In locations like Orca Inlet ground discharge of fish waste is not only deleterious but may also substantially reduce fish production by hindering natural recycling.