Marine Food Chains/Webs Energy from primary production is transferred up the trophic chain Each step is inefficient (~90% energy is lost) Shorter chains are more efficient at producing apex predators

It ’ s a web, not a chain

Marine Food Chains/Webs Energy from primary production is transferred up the trophic chain Each step is inefficient (~90% energy is lost) Shorter chains are more efficient at producing apex predators (harvestable fish)

Bottom Up Estimates of Fish Production Fish production is equal to the PP multiplied by the efficiency of exchange for each trophic level Ex: 3 trophic level system Fish Prod = TotPP * eff1 * eff2 Ex: 6 trophic level system Fish Prod = TotPP * eff1 * eff2 * eff3 * eff4 * eff5 Efficiencies are small (~10%) so most PP is lost

CalCoFI Primary Production Estimated PP from ocean color imagery Used a bio-optical algorithm (VGPM) Compared results to PP observations from CalCoFI Kahru & Mitchell [2002]

CalCoFI Primary Production r 2 = 0.59

0-100 km Total nearshore PP = 8x10 12 gC mo -1 ~1x10 14 gC y -1

CalCoFI Primary Production Satellite estimates of PP show fair validity to observations Seasonal cycle is obvious Total nearshore PP ~ 8x10 12 gC month -1 ~ 1x10 14 gC year -1 How many tons of fish are produced?

Bottom Up Estimates of Fish Production Fish production is equal to the PP multiplied by the efficiency of exchange for each trophic level Ex: 3 trophic level system Fish Prod = TotPP * eff1 * eff2 Ex: 6 trophic level system Fish Prod = TotPP * eff1 * eff2 * eff3 * eff4 * eff5 Efficiencies are small (~10%) so most PP is lost

Bottom Up Estimates of CA Current Sardine Production So Cal Bight – Int PP ~ 1x10 14 gC year -1 Focus on clupeid fish (cf., sardines) This food chain PP energy goes to fish in 2 steps

Bottom Up Estimates of CA Current Sardine Production Clupeid Fish Prod = Tot_PP * Eff1 * Eff2 = (1x10 14 gC year -1 ) (0.1) (0.1) = 1x10 12 gC y -1 Fish are not made of just carbon – Wet weight is ~10% carbon Annual Clupeid Fish Prod = 1x10 13 g Fish = 10x10 6 Mt

Spawning biomass is roughly the same as our fish production guestimate Sardine Stock Assessment from CFG 1,000,000 Mt/y Sardine biomass is 10% of possible fish production

10,000,000 Mt/y

Sardine landings ~ 1% Total Clupeid Fish Production 100,000 Mt/y

Bottom Up Estimates of Fish Production Open ocean total PP ~ 50x10 15 gC year -1 Focus on tuna in an open ocean food chain This food chain PP energy goes to tuna in 5 steps

Bottom Up Estimates of Global Tuna Production Global Tuna Production = = Tot_PP * Eff1 * Eff2 * Eff3 * Eff4 * Eff5 = (50x10 15 gC year -1 ) (0.1) 5 = 5x10 11 gC y -1 Taking into account wet weight Annual Maximum Tuna Production = 5x10 12 g Fish = 5,000,000 Mt/y Global catch for “tunas” is ~6x10 6 Mt/y (FAO)

WARM COOL Switching between Sardine & Anchovy

Varved Sediments in Santa Barbara Basin

The Santa Barbara Basin is nearly anoxic Sill depth

Varved Sediments in Santa Barbara Basin Sediments form in annual varves Low O2 – little bioturbation – require C inputs

Respiration & Remineralization remineralizers h CO 2 O2O2 NUTS Biological processes consume plants & O 2 to make CO 2 & nutrients sinking organic matter

Varve Formation Varve formation requires high inputs of sinking carbon to suck up O 2 Example from Santa Monica Basin

Fish Abundance from Varves Fish scales are ID ’ ed & counted Annual varves are dated Results in fish scale deposition rate Correlated to fishery biomass records to produce a 1700 year biomass time series

Epochs of sardine dominance…

Fish Abundance from Varves Switching between anchovy & sardine is seen – on 20 to 50 year time scales Policy implications are important – Fishery collapses are not JUST due to fishing – Climate control of fish abundances

Fish Production in CA Current Bottom up controls of fish production Some consistency with fishery statistics Hard to use alone to predict harvest quotas – BUT sets an UPPER bound Switching of stocks & climate control – Only one clupeid fish fills niche (sardine OR anchovy) – Who it is is controlled by climate (PDO; cool/warm)