SIO 296: January 15, 2010 Highly Migratory Species: Research and Management

1. SIO 296: January 15, 2010Highly Migratory Species: Research and Management SWFSC HMS Biology and Population Dynamics Group Antonella Preti John Childers Owyn Snodgrass Stephanie Snyder Heidi Dewar Natalie Spear James Wraith Candan Soykan Steve Teo Russ Vetter John Hyde Amber Michaud

2. Lecture Outline • Management Framework in the Pacific for Highly Migratory Large Pelagic Fish (Tuna and Tuna-like Species) • Bycatch Issues • Stock Structure • Ecosystem Considerations • Foraging Ecology Lab/Dissection

3. International Management • IATTC: Advised by their scientific staff with input from scientists and delegates of member nations • WCPFC: Advised for the North Pacific by working groups of the International Scientific Committee (ISC) made up of scientists from member nations

6. Albacore (Thunnus alalunga) Bluefin Tuna (T. orientalis) Yellowfin Tuna (T. albacares) Bigeye Tuna (T. obesus) Skipjack (Katsuwonus pelamis) Dorado (Coryphaena hippurus) Swordfish (Xiphias gladius) Striped Marlin (Tetrapturus audax) Shortfin Mako Shark (Isurus oxyrinchus) Thresher Sharks (Alopias spp.) Blue Shark (Prionace glauca) Transboundary Large Pelagic Fish

7. Domestic Management • Regional Fishery Management Councils: PFMC, WPFMC • HMS Management Plan since 2004 • Advised by: a management team made up of State and Federal representatives including scientists (HMSMT); a scientific and statistical committee (SSC); a subpanel of constituents from the commercial and recreational fisheries industries and NGOs (HMSAS); the public • State Agencies: CA, OR, WA • Advised by their staff with input from constituent groups and the public

8. Bycatch The issue… • Fisheries for tuna and other highly migratory species are often constrained by the incidental take of vulnerable non-target species. Even fisheries that target productive, healthy stocks can face restrictions if interactions with protected species occur. Examples for HMS in the Pacific include 1) the closure of coastal CA waters to drift gillnet gear out to 75 miles during the spring to protect reproductive female thresher sharks, and 2) the 2001-2004 closure of the Hawaii shallow-set longline fishery in the North Pacific due to turtle interactions.

9. Bycatch • The species • Mammals, turtles, birds, sharks, vulnerable life stages of target fish, other fish

10. Bycatch • Conservation measures: Sharks, sea turtles, seabirds, juvenile fish IATTC (see www.iattc.org/ResolutionsActiveENG.htm) WCPFC (see www.wcpfc.int/conservation-and-management-measures)

11. Bycatch quantification: observer programs, logbooks, landings receipts Data suggest that longline gear catches fewer non-target fish for each swordfish caught.

12. Gear Modifications • Using corrodible links to reduce trailing tackle on thresher sharks • Testing rare earth metals to deter sharks • Using circle hooks to prevent swallowing and esophogeal damage Preliminary results from Wang, Swimmer and Hutchinson, PIFSC

13. TurtleWatch – predicting turtle distribution from SST Based on two decades of loggerhead turtle satellite tracking and fishery effort data. See Howell et al., Endangered Species Research, 2008.

14. Stock Structure The issue… Are there discrete populations that should be parameterized separately in the stock assessments and managed separately? Do individual fisheries exploit a single or multiple sub-stocks?

15. Tools for Examining Stock Structure Tagging Genetics Parasites Morphology/life history Fishery dynamics Otolith Microchemistry

16. Trans-Pacific (n=1) North-Central-South (n=3) Overwinter Baja (n=7) North-Central-North (n=5) South-Central-South (n=4) Albacore movements, mixing and stock structure: 20 fish, 5 migratory patterns

17. Chile I Chile II Relative frequencies of mitochondrial haplotypes found for shortfin makos throughout the Pacific. Significant differences were found between north and south Pacific populations. Genetics: RFLP, mtDNA, microsatellites

18. Stock Structure • Otolith Microchemistry Used as a technique to differentiate stocks and reconstruct the migratory history of individual fish. Otoliths precipitate with growth and elements are integrated into the aragonite protein matrix. Otoliths are metabolically inert; resorption or remobilization of newly deposited elements is negligible. The chemical composition of otoliths (e.g. SR:Ca ratios and others) serve as natural tags or chemical signatures that reflect the chemical composition of the individual’s habitats over time.

19. Stock Structure From Laurs and Wetherall, 1981 “wrinkle belly” swordfish with cookie cutter shark bite • Parasites • Morphology/life history • Growth rates • Skin morphology • Fishery dynamics

20. Ecosystem Considerations Spatial and Temporal variation in behavior and distribution Oceanographic influences Multi-species associations Foraging Ecology

21. Site Specific Behavior

22. Interannual Variations Movements of CA sea lions tagged in 2003 and 2004. From Weise et al. 2006 2003 2004

23. Niche partitioning among co-occurring species Mako Thresher Coastal Pelagics Cephalopods Blue Other Teleosts

24. Wrap up: based on our concluding discussions • We should consider adaptive management strategies due to spatial and temporal variation in the behavior in target and bycatch species • We should strive for predictive models that will help to forecast fluctuations in availabilty in order to establish effective harvest guidelines • Closing fisheries is not always the best way to mitigate bycatch: e.g. transfer effect

25. Excercise • Compare diets of two predators, A and B, collected by observers in the CA drift gillnet fishery • Calculate %Number, %Weight, %Frequency of Occurrence (%FO), Geometric Index of Importance (GII) and Index of Relative Importance (IRI) for each prey to determine its contributions to the diet of each predator • Calculate the Schoener’s Index of dietary overlap for the 2 predators • If I told you these were 2 different predators collected in overlapping time and space, what conclusions would you draw? • If I told you this is one predator but sampled in two different years, fall 1998 and fall 1999, what conclusions would you draw?

26. Exercise cont., formulas %Ni = (Number of preyi)/(Total Number of all prey)*100 %Wi = (Weight of preyi)/Total Weight of all prey)*100 %FOi = (Number of stomachs containing preyi)/ Total Number of stomachs containing any prey)*100 GIIi = (%Ni+ %Wi +%FOi)/ IRIi = (%Ni + %Wi) * %FOi Schoener’s Index = CAB = 1 – 0.5(Σ │%NiA /100- %NiB/100 │)