8:35 John Ford, resident KW foraging ecology
What may have caused the simultaneous declines in the N and S residents during the late 1990s? Nutritional stress?
We compared expected and observed births and deaths, where expectations were based on period of unlimited growth (’73-’90). There were two phases of increased mortality in adult/juvenile fe/males: late 90s for N and S, mid-80s for southern and A pods.
Sockeye outnumber Chinook by 1000x in areas where residents forage during the summer. Yet Sockeye make up less than 1% of diet during sampling period (May-Oct). Only adult males don’t bring prey (of all species) to the surface for sharing. This indicates that our surface prey fragment sampling technique isn’t biased. Additionally, sockeye swim shallow and Chinook deep, but we’ve only sampled 3 sockeye predation events.
Sub-adults show some preference for smaller fish like Pink and Chum that make up about about 20% of their diet. Recent winter sampling show continued chinook preference: 2 samples in Jan from N residents; 2 from J pod near Nanaimo Chinook. They didn’t see enhanced mortality in weaners (expected in mammals under nutritional stress), perhaps because of prey sharing. Mortality lags chinook abundance by 1 year.
The Chinook abundance index is a bit below average currently, so we expect high mortalities next year. A research priority is to identify important Chinook stocks for whales (Brian Gisborn, Brad Hanson). How many are hatchery fish?
9:01 Jennifer (for Brad), species and stock ID for southern residents
Goals were to supplement Ford’s prey samples (beyond J pod), to collect fecal/regurgitation samples (to avoid potential bias in surface fragment sampling), and to define foraging surface behavior. We now have ~150 fecal samples and 250 foraging samples that have been analyzed genetically.
Feces were screened for rockfish, sole, starry flounder, pacific halibut, Irish lords, herring, sculpin, sable fish, greenling, lingcod, cabezon, and squid. Thus far, we have detected (rarely) rockfish, sole, Pacific halibut, and lingcod.
Prey sampling results — Steelhead may be imporant in May. Chinook dominate from May-September.
Fecal sampling results — Chinook dominate in May-September, but Chum is also important in September.
Breakdown of Chinook stocks is based on GAPS database which gives genetic profile for each river from 20k sampled fish. They appear to be eating Chinook in rough proportion to what is available (most dense by number? biomass?).
Future work is focused on bioenergetics (how many fish do they consume and do they impact the stocks?) and availability (Is background noise impeding foraging efficiency?). We need samples in Sept-Dec and May!
Eric Ward, risk analysis
Developed a fecundity model which was age specific (the rate of maturity is much faster than rate reproductive senesence). Extrinsic factors were prey, contaminants, anthropogenic events (oil spills). Can’t assess oil spill risks and disease risks (due to lack of data), nor do extant data help us characterize the variability of fecundity between sub-populations (e.g. pods) and indivduals.
Used Pacific Fisheries Management Council (PFMC) indices (terminal run) from to characterize prey. Also look at Pacific Salmon Commission (PSC) relative index. Ballard locks was used to get a U.S. sockeye time series to compare with the big (25 million) Fraser sockeye runs. Used ENSO and PDO time series to characterize climatic variability.
Is the SR production different from NR? It looks similar (~90+% of NR production rate). High probability of prey (Chinook) correlates highly w/fecundity. Late run Fraser and Oregon coastal stocks are driving the correlation of the prey variable.