Some basics and a bit about small pelagics

1. Some basics and a bit about small pelagics March 30, 2010 FISH/ENVIR 330C

2. announcements • Please turn in your 1st day survey • Lab assignment #1 is due Friday, 10:30am • Either hand it in to Paul or use the on-line assignment drop box • 1st reading/lecture quiz is Friday, 10:30-10:40 (don’t be late)

3. Fisheries Science • Marine ecosystems are difficult to observe • Multiple trophic levels may lie between primary producers (phytoplankton) and economically, socially, or culturally valuable organisms (cod, sea birds, whales, etc.) • And there is also the physical and chemical environment that is changing …

4. Space-Time Scales of Ocean Processes(Mantua et al. 2002, U.S GLOBEC issue of Oceanography) Human caused climate change Human caused climate change centuries Aleutian Low NorPac High decades Boundary currents decades years seasons Upwelling fronts seasons eddies Time (seconds) days days Surface Mixed layer convection hours hours turbulence seconds Tide pool fjord Ocean gyres Bay/estuary Space (meters)

5. data collection • What we see are generally bits and pieces of information related to ecosystem states and processes • It is far easier to observe terrestrial and freshwater systems

6. Astoria 4 6 ° N Tillamook 4 5 ° N + + + + Newport 50m 100m 4 4 ° N 150m Coos Bay 4 3 ° N 4 2 ° N 125° W 124° W 123° W 200m • NH-Line Hydrographic and Zooplankton • Time Series 100m 50m • Bi-weekly Sampling: • 1969 – 1973 (Miller, Pearcy, Peterson) • 1983 (Miller, Batchelder, Pearcy, Brodeur) • 1990-1992 (Fessenden and Cowles) • 1996 – present (Peterson et al.) NH Line Provided by Bill Peterson, NOAA Newport

7. Sampling methods • Water sampling with CTD, Niskin Bottles, and buckets for hydrography, chl-a and nutrients • Mesozooplankton with ½ m 200 um net towed vertically • Euphausiids with 70 cm 505 um net towed obliquely Provided by Bill Peterson

8. Collecting long-term perspectives on zooplankton composition and abundance takes a lot of TIME and EFFORT • There is a strong inverse relationship between northern (boreal) and southern (subtropical) copepod species • changes are rapid and approach order of magnitude differences among years 99 02 92 69-73 83 97 98 Southern Copepod Northern Copepod Log10(Biomass anomaly) log110(Biomass anomaly) Modified from Bill Peterson’s original

9. Pacific halibut recruitment lots of valuable data, in this case “recruitment” estimates come from fishery landings and surveys From: IPHC Stock Assessment Reports http://earthguide.ucsd.edu/DFL_ed_prelim/kinds/kinds_commercial.html

10. Recruitment • Recruitment refers to the quantity of younger fish surviving the various egg, larval, and juvenile stages to begin to be captured in a fishery. • Lots of interesting and important things happen prior to recruitment, in fact a whole series of continuous events that typically winnows down extremely large numbers of eggs and larvae into a much smaller number of recruits • The same physical process may affect survival in different ways at different stages of “pre-recruit” development

11. Recruitment • Before recruitment, the target organisms are essentially invisible to humans because they are not taken by any fishery, (though sometimes taken in “pre-recruit” surveys) • The conventional paradigm of fisheries science is to aggregate the rich ecology of the pre-recruit period into this single quantity -- recruitment

12. Stock-Recruit relationships tend to be very noisy • The deviations of the data points from the model (shown by the curve) are often referred to as environmental noise • This “noise” poses major challenges for fishers and fishery managers Total recruits (7 year olds) Effective spawning biomass

13. The comparative approach: seeking signals in the noise • Controlled experiments, like those in a laboratory setting, are simply not possible for large marine ecosystems

14. The comparative method offers a valuable alternative West Coast of N. America • Here, examine separate realizations needed for scientific inference via recognition of informative patterns in natural phenomena • different sets of seasonal or geographic settings, encompassing a range of natural variability in conditions and mechanism, replace experimental treatments West Coast of S. America

15. Inherent limitations • Comparative results generally conform to the information available at the time they are produced • In this realm, we are continuously faced with the challenge of separating mechanistic causality from outcomes based on history and happenstance

16. The pelagic reproductive strategy • Upwelling zones are among the most productive in the world, with some of the largest fish populations • Classic examples lie along the eastern edges of ocean basins All are known for their rich fisheries and very large populations of small pelagic fish stocks like sardines and anchovies Bakun and Nelson, 1991, J. Phys. Oc.

17. The pelagic reproductive strategy • Upwelling zones are great places for feeding, yet difficult habitats for reproduction • Major pelagic fish stocks feeding in the upwelling region undertake extensive spawning migrations in order to avoid placing their larvae in the upwelling zone where they would tend to be swept offshore and dispersed into the open ocean

18. Critter of the Day Sardinops sagax caerulea California pilchard, Pacific sardine, Sardina Monterrey Family: CLUPEIDAE (Herrings and Sardines) Image from: http://www.oceanoasis.org/fieldguide/sard-cae.html

19. Pacific sardines • maximum age: 12 • age of maturity: 2 • age of recruitment: 1 • prey: diatoms, copepods, euphausiids • predators: fish, tuna, sea-birds Large adults Adults Summer feeding Juveniles Spawning (Feb-April)

20. Processes impacting reproduction • Temperature: • warm years; spawning shifts north • development of larvae favoured between 14-160C • Stratification: • concentrating prey for first feeding larvae • Fronts and Meanders: • concentrate food for larvae • Bloom intensity: • spawning in highly productive areas Spawning (Feb-April) Slide provided by Sandy McFarlane, DFO

21. 1950’s crash in California’s sardinesthe end of “cannery row” Limited fishery opened Fishery closed Barnes, et al. 1992

22. Pacific Sardines: a history of 20th Century boom and bust cycles(Kawasaki and Omori 1988)

23. Andy Soutar with a Kasten Core from the Santa Barbara Basin Image from http://www.mbari.org/news/news_releases/2006/forams-images.html A section of a sediment core from the Santa Barbara Channel showing annual sediment layers laid down each year Image credit: 2005 David Field

24. 2000 year history of California sardine abundance Biomass (106 metric tons) Years before present Baumgartner, et al. 1992

25. The pelagic strategy puzzle • Because of the reproductive difficulties caused by the disruptive upwelling environment, some suggest that pelagic fish in these regions seldom approach the carrying capacity of their adult habitat • So why are anchovies, sardines, and other species that spawn pelagic eggs and larvae dominant species in these regions where loss of reproductive products appears to be such a problem? • Even more puzzling is the success of the pelagic reproductive strategy among fishes and invertebrates inhabiting ocean islands and banks. Tropical fish typically posses reproductive habits and behaviors that seem explicitly adapted to cause eggs and larvae to be quickly transported offshore, where they would be most subject to loss.

26. reminders • 1st day survey is due • Assignment #1 due Friday at 10:30am • 1st reading/lecture quiz on Friday at the beginning of class (10:30-10:40) … don’t be late