1. Utilization of Attack Marks as a Proxy for Lamprey Distribution and Abundance in the Bering Sea Kevin A. Siwicke, Trent M. Sutton, and Andrew C. Seitz University of Alaska Fairbanks • School of Fisheries and Ocean Sciences • kasiwicke@alaska.edu Introduction Results (cont.) Analysis Methods • Arctic lamprey (Lethenteroncamtschaticum) and Pacific lamprey (Lampetratridentata) are important in food webs1, and they parasitize several commercially important fishes2 • Parasitic lamprey interactions can have individual- and population-level effects (e.g., Great Lakes3) • In the Pacific Northwest, Pacific lampreys are culturally important to numerous native groups4, and in Alaska there is a subsistence and commercial harvest of Arctic lampreys on the lower Yukon River5 • In Alaska, lamprey ranges6 (Fig. 1) overlap in the Eastern Bering Sea (EBS), coinciding with a broad coverage of Pacific cod (Gadusmacrocephalus), a common lamprey host • To date, there is a paucity of research focused on the parasitic-marine phase of lampreys, and thus a lack of basic ecological knowledge about them • To study basic ecological information about lampreys, we use recent lamprey attack marks on Pacific cod as a proxy for capturing lampreys • Photograph Analysis • Marks were classified as A (penetrating muscle) or B (not penetrating muscle) and stage 1-4 (where 1 = no healing and 4 = completely healed7; Fig. 2) • Multiple marks without a link were counted as separate attacks8 • Diameter of mark was measured (mm) using the scale in the photograph • “Recent” attack refers only to stage 1 and stage 2 marks # of Attacks # of Pacific Cod Captured Fig. 3. Linear regression model of recentlamprey attacks with respect to the number of Pacific cod captured (regression line shown in black). Pacific Arctic Frequency Fig. 2. Lamprey marks on Pacific cod from the Bering Sea where (a) multiple type-A wounds, (b) B-2, (c) A-2 with sliding, (d) type-B slide, (e) A-3, and (f) A-4. John Rowley - Gourmet.com • Objectives • Using recent lamprey attack marks on Pacific cod, we will: • Examine the distribution of Arctic and Pacific lampreys in the EBS using geographic location of recent attack marks • Examine the relative abundance of Arctic and Pacific lampreys in the EBS, using frequency of recent attack marks • Examine recent lamprey attack mark diameter to assess feasibility of elucidating species-specific attack marks • Assumptions • Attack mark frequency isproportional to lamprey abundance • When no host fish are caught, no lampreys are present • All hosts with stage-1 and stage-2 marks (recent) were attacked in the immediate vicinity of catch • Host fishes attacked by lampreys and hosts not attacked by lampreys have the same probability of being caught • Data Analysis • Map recentattack frequency in a GIS framework • Determine if there is a linear relationship between number of captured P. cod and recent attack marks • Plot frequency distribution of recent attack mark diameter Attack Mark Diameter (mm) Fig. 4. Diameter (mm) frequency of recentattack marks from lamprey documented on Pacific cod, where each bar represents 5 mm categories. Brackets indicate mark diameters most likely associated with respective species based on published ratios of oral disc diameter to total length. Field Methods Discussion • In the EBS, 125 stations were sampled for P. cod (Fig. 1) • For each station, there were six skates with 100 hooks per skate • Total length was measured on the first 15 P. cod per skate • From those measured, fish with lamprey attack marks were photographed • There appear to be areas of relatively high lamprey concentrations in the EBS, suggesting preferential lamprey feeding grounds • The relationship between attacks and number of P. cod captured is weak (R2 = 0.15), suggesting that other factors such as water temperature, depth and lamprey abundance may also be important • The broad range of attack mark diameter may include attacks by several year classes of both Arctic and Pacific lampreys, and the mid-range diameters will need to be examined further Preliminary Results • P. cod were caught at 111 of 125 stations, of which P. cod with lamprey attack marks were captured at 63 (Fig. 1) • 4,104 P. cod were measured and 202 had lamprey attack marks • 292 separate attacks were identified, of which 241 (5.87 per 100 cod captured) were recentattacks • Geographic extent of recentlamprey attacks on P. cod varies across the sampled region (Fig. 1) • The number of documented recent attacks increased with the number of P. cod captured (p-value = 8.94x10-6, R2 = 0.15; Fig. 3) • Mean ± SE of recentattack mark diameter was 22.0 ± 0.7 mm (range from 2–51 mm; Fig. 4) Fig. 1. Publishedranges of marine-phase lamprey in Alaska shown (right). Red inset expanded showing P. cod sampling stations, coded by frequency of “healed” and “recent” attacks. Yellow ellipses highlightareas of relatively high attacks. Future • Sample all P. cod and halibut from all stations of the 2012 IPHC annual setline survey ranging from CA to AK • Examine distribution and abundance of Pacific and Arctic lampreys in the eastern north Pacific, and examine how environmental correlates, such as water temperature and depth, affect them • Refine species differentiation of Pacific and Arctic lampreys, based on attack mark diameter • Examine survivorship of host fishes using attack mark parameters Acknowledgements: We would like to thank the IPHC and NMFS for photographing cod for this project. We would also like to thank UAF, NSF and MESAS/SELMR for their support. (Composite Image)