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Pinniped Research: Insights into Marine Ecosystem Changes

Discover the extensive research by CEMP on pinniped species like Fur, Elephant, Weddell, and Leopards seals. Data collected covers predator performance, trophic links, ecology, and more. Explore the unique and valuable insights gathered over decades.

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Pinniped Research: Insights into Marine Ecosystem Changes

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  1. US-AMLR Datasets Pinniped research Mike Goebel

  2. CEMP was established in 1984 in response to a developing krill fishery to: • “detect and record significant changes in critical components of the marine ecosystem ……” • “distinguish between changes due to harvesting of commercial species and changes due to environmental variability, both physical and biological.” CCAMLR Ecosystem Monitoring Program

  3. Pinniped species studied by US-AMLR • Fur seal • Elephant seal • Weddells • Leopards

  4. Predator performance – Fur seals • Summer (Local/Regional scale) • Foraging success (4 indices, inc. trip duration*) • Trophic links – food web & diet studies (5) • Reproductive success (4, inc. pup growth*) • Winter (Scotia Sea - broader geographic scale) • Annual survival , natality (4 indices) • Pup production (2 indices) • Arrival condition – timing of reproduction (2) • Multi-year • Demography - Population vital rates • Age at first reproduction • Net reproductive rate • Mean generation time • Intrinsic rate of growth *CEMP Indices

  5. Datasets collected – Pinnipeds • Data sets - Annual (1997/98 – Present): • DEMOGRAPHY - Mark-resight tag database • Adult females tagged 12-15% (3% Cape-wide) • Known-age 94% • Pregnancy and survival rates • 500 pups tagged annually* (~7% of pup production) • ECOLOGY • TDR deployments (Dec-Feb) • PTT/GPS deployments – (Dec, Jan, Feb) • Trip duration (CEMP) • Pup growth* (CEMP) • TROPHIC LINKS (Scats, Fatty acids, & Stable isotopes) • OTHER PINNIPEDS: • Mark resight data – leopards & elephant seals • Weaning mass – elephant seals Data sets - Periodic: ECOLOGY – Regional surveys (SSMUs) (1986, 1991, 1995, 2001, 2006) OCEANOGRAPHY - large seals as samplers – CTD* (2005-2009) * In collaboration with UCSC (NSF – funded) * In collaboration with Chile

  6. Fur seal population vital rates • Age-specific mortality • Net reproductive rate • Mean generation time • Intrinsic rate of growth • Age at 1st reproduction (AFR) • Adult females • survival: High • pregnancy rate: High • Juveniles • first year survival: Low • ~90% mortality by AFR

  7. 1999/00 Tooth data: 1982-1997 year classes Mark-resight data: 1998-2006 year classes Fur seal year class success 1982-2006 Recruitment and/or survival are variable ….that characteristic has not changed over three decades

  8. Krill demographics & fur seal performance Krill maturity & sex ratio Krill length in fur seal diet Fur seal trip duration • Trip durations are shortest when: • Krill length is >47mm • Low proportion of juvenile krill • High proportion of female krill

  9. Fur seal performance Assessing overall fur seal performance: an ordination approach using 17 indices • Fur seal performance was best 2000-2002 & 2006 when: • Krill length was >47mm • Low proportion of juvenile krill • High proportion of female krill

  10. Top-down impact on fur seal populations: 28-50% of all fur seal pups consumed by mid-Feb

  11. Fur seal phenology: Climate change effects? Trends in arrival and parturition for female fur seals Arrival and date of birth are becoming earlier.

  12. Uniqueness of US-AMLR pinniped datasets • Number of indices, length of time series, having a large known age population, and a large mark-resight database • Demography & vital rates for an Otariid • Data are collected simultaneously with offshore data • Leopard seal data • Data sets are collected in a rapidly changing environment • Colonizing events

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