SIO 296: January 15, 2010 Highly Migratory Species: Research and Management SWFSC HMS Biology and Population Dynamics Group Antonella PretiJohn Childers Owyn SnodgrassStephanie Snyder Heidi DewarNatalie Spear James WraithCandan Soykan Steve TeoRuss Vetter John HydeAmber Michaud

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 Lecture Outline

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

Transboundary Large Pelagic Fish 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)

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

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 closure of the Hawaii shallow-set longline fishery in the North Pacific due to turtle interactions.

Bycatch The species – Mammals, turtles, birds, sharks, vulnerable life stages of target fish, other fish

Bycatch Conservation measures: Sharks, sea turtles, seabirds, juvenile fish IATTC (see WCPFC (see

Bycatch quantification: observer programs, logbooks, landings receipts Catch of the major finfish species for all observed DGN sets 1990 through Jan Number of sets is Catch of the major finfish species for all observed CA-based SSLL sets, October 2001 through February Number of sets is 469. Species Total Observed Catch Catch per 100 Swordfish Catch of Swordfish per 100 Finfish Species Total Observed Catch Catch per 100 Swordfish Catch of Swordfish per 100 Finfish Mola, Common49, Shark, Blue5, Shark, Blue21, Albacore ,633 Albacore16, Shark, Shortfin Mako ,017 Tuna, Skipjack9, Longnose Lancetfish ,197 Shark, Shortfin Mako7, Tuna, Bigeye ,369 Mackerel, Pacific6, Escolar ,872 Shark, Common Thresher 5, Stingray, Pelagic ,010 Opah4, Oilfish861.18,735 Tuna, Bluefin3, Dorado ,557 Mackerel, Bullet3, Mola, Common ,729 All Others5, All Others ,912 Swordfish, Broadbill16,646Swordfish, Broadbill7,512 Data suggest that longline gear catches fewer non-target fish for each swordfish caught.

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

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.

Stock Structure 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? The issue…

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

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

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

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.

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

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

Site Specific Behavior

Interannual Variations 2003 Movements of CA sea lions tagged in 2003 and From Weise et al

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

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

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?

Exercise cont., formulas %N i = (Number of prey i )/(Total Number of all prey)*100 %W i = (Weight of prey i )/Total Weight of all prey)*100 %FO i = (Number of stomachs containing prey i )/ Total Number of stomachs containing any prey)*100 GII i = (%N i + %W i +%FO i )/ IRI i = (%N i + %W i ) * %FO i Schoener’s Index = C AB = 1 – 0.5(Σ │%N iA /100- %N iB /100 │)