Salmon phishing in the Gulf of Alaska

Transcription

1 Salmon phishing in the Gulf of Alaska An archaeological ig in the North Pacific Survey ata ( ) Skip McKinnell, PICES James C. Christian, Fisheries & Oceans Canaa Nancy D. Davis, University of Washington Davi L. Mackas, Fisheries & Oceans Canaa

2 Motivation Pacific humans eat Pacific salmon. Pacific salmon eat shelle pteropos. Measurable CO2 increases are causing measurable ph eclines in the North Pacific. Pteropo shells issolve in low ph water. So what?

3 sockeye humpback chum coho chinook Preominantly planktivorous Pacific salmon (encircle)

4 Aragonite saturation epths Source: Feely et al. (2004)

5 FRBC North Pacific Survey Fisheries Research Boar of Canaa ( ) Deploye 4 ocean-going salmon fishing vessels Salmon age, sex, length, weight (n 2000 per year) Zooplankton (vertical net tows from 150m to surface) Sea surface temperature an salinity > salmon stomachs examine for prey types. One naval vessel geare for oceanography. Bottle casts Bathythermograph traces ph measure in fall/winter of 1956/57 Nutrients Plankton Before 2-3 billion salmon (annually) release from hatcheries.

6 Humpback salmon growth at sea Salmon growth is ensity-epenent Ocean entry First autumn (5 mo.) Maturity (14 mo.) 4 cm 13 cm cm

7 Gulf of Alaska salmon iets Chum Coho Humpback Sockeye Data source: Fisheries Research Boar of Canaa

8 Limacina in salmon iets ( ) 0.15 P ro p o rtio n o f fo o Humpback Chum Sockeye 0.10 Highest fractions (~15%) of Limacina in iets occurre in humpback salmon in April, iminishing to 8% by August. Sockeye & chum salmon iets have little (~1%) Limacina in April, increasing (~3%) through the growing season Not foun in winter sampling Month 8 10 Data source: Fisheries Research Boar of Canaa

9 Seasonal Cycles at Station P mg / m Pteropoa Copepoa Month Data source: McKinnell & Mackas (640 tows) Copepos are ominant in the plankton Pteropo biomass peak is 1 mo. earlier than copepo peak Pteropo abunance persists in surface waters

10 Humpback Salmon iets Northwest Pacific Chum Percent pteropos (purple) Infrequent in sockeye an humpback salmon >25% of chum salmon iet + increasing tren Limacina eaten when higher quality foos not available Source: Karpenko (2007) NPAFC Bulletin 4 Sockeye

11 Dateline (180º) transect salmon iets h Fis oa p ro e Pt a a a sii o po ipo pep au a ph ph ec o u m D C E A h mp a p Co e po a c De a po E a h up a ii us h Fis oa op er t P u i Sq ntifie e i Un h Fis oa op er Pt Prey ui Sq ntifie ie n U 0.5 ph Am Sockeye Humpback Chum Coho a a a sii ipo pepo capo hau ph p e o u m D C E A Data Source: Masahie Kaeriyama, Hokkaio ip o a p Co ep ii a us po ha ca p e D Eu o a 2.0 Prey h F is o a op er t P u i ie f nt i i e n U Sq Prey Sockeye Humpback Chum Coho ip o 2.0 Sockeye Humpback Chum Coho a oa a sii ipo pepo cap au ph ph e o u m D C E A 0.5 A Prey Cumulative proportion Cumulative proportion ui Sq ntifie ie n U Sockeye Humpback Chum Coho 1.5 Cumulative proportion Sockeye Humpback Chum Coho Cumulative proportion Sockeye Humpback Chum Coho Cumulative proportion Cumulative proportion h Fis oa op er Pt Prey ui Sq ntifie ie n U a oa a sii ipo pepo cap au ph ph e o u m D C E A h Fis oa op er Pt Prey ui Sq ntifie e i Un

12 Prince William Soun

13 Juvenile humpback salmon Prince William Soun hatcheries 50 Pink salmon grew faster in 2002, 2004 Marine survival higher for releases in 2002, 2004 than in 2001, 2003 Diets in August in 2002, 2004 ha greater fractions of (pteropos+oikopleura) But iets in 2001 ha high fractions of pteropos but low survival (next slie) Data source: Cross et al % WEIGHT 8-9% YEAR MONTH 9 10

14 Gulf of Alaska Shelf Juvenile humpback salmon iets Interannual Diet Comparison: August GAK 1-6 n=36 n=28 n=80 n=52 n=82 n=50 100% Other* Diet as %Prey WT 80% Insects Fish Larvaceans 60% Pteropos (Limacina) Crab/Shrimp 40% Hyperii Amphipos Euphausiis 20% Large Copepos Small Copepos 0% Year Source: US GLOBEC

15 Present Day Commercial Catch Tonnes (x 1000) Data: NPAFC Year

16 Summary 1. Pacific salmon an pteropos share ocean habitats that are among the most threatene by ocean aciification. 2. They have live together in this habitat for millennia 3. Pacific salmon, augmente by hatchery releases, are currently very abunant. 4. The exception is the California Current upwelling system, but here salmon survival is worse when upwelling is iminishe.

17 Review of ieas an ata In general, the pelagic Pacific salmon have varie iets. The presence of pteropos (primarily Limacina) in their iet varies among species by life history (evelopmental) stage of salmon by season an by year by region Chum salmon in the NW Pacific have >25% Limacina in their iets an the tren was increasing over 5 ecaes. Limacina an Oikopleura are sai to be critical to growth an survival of juvenile humpback salmon in Prince William Soun Humpback salmon generally eat what their environment provies, but occasionally not; in the Gulf of Alaska pteropos forme 15% of the iets in April uring the late 1950s an 1960s. At this point in history, the abunance of hatchery-reare salmon has ha a greater effect on Limacina abunance than OA.

18 Salmon is of vital importance to the Inians; we nee only cut them off from their salmon fisheries to have them completely at our mercy. John Keast Lor (1866) This 150 year ol opinion reflects the importance of Pacific salmon to Pacific culture an shoul form at least part of the basis for concern about the effects of an increasingly aciic ocean. Neglect is unacceptable.

19 What to o? Multi-national science program on NPacOA Coastal/shelf an basin components where the basin component has a sampling frequency greater than once/century. Improve technology for monitoring oceanic carbonate system. Improve knowlege of life histories an ecological roles of the key players in the OA issue. Exten/focus salmon iet stuies on OA issue When an where o corrosive waters create corroe pteropos? Genomics component. Trophoynamic moels embee in carbonate-parameterise global ocean/atmosphere moels. Communication OA as a sleeper issue of global change ph is a scientific scale; use a metric an language that resonates with the public Ecological Dow-Jones

20 Pteropo abunance in BC Coastal pteropo abunance varies logarithmically from year to year Lowest observe values in ~30 years occurre in 2007 Source: D.L. Mackas, Institute of Ocean Sciences