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Monsters? Or are we Mythtaken?

Monsters? Or are we Mythtaken?. Jean F. McKinnon Department of Marine Science, University of Otago. Photo by Kerry Perkins. What interests me?. SNAILS????. Yes! Squid are molluscs, (in the same family as snails and clams) but they live like fish!. How do they fit into the ecosystem?

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Monsters? Or are we Mythtaken?

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  1. Monsters?Or are we Mythtaken? Jean F. McKinnon Department of Marine Science, University of Otago Photo by Kerry Perkins Seaweek 2006

  2. What interests me? Seaweek 2006

  3. SNAILS???? Seaweek 2006

  4. Yes! Squid are molluscs, (in the same family as snails and clams) but they live like fish! Seaweek 2006

  5. How do they fit into the ecosystem? • What do they eat? • How long do they live? And how fast can they grow? • When do they breed? • Do they migrate? Seaweek 2006

  6. How long do they live and how fast do they grow? • What do they eat? Seaweek 2006

  7. Arrow Squid are an important fishery species in NZ. • 2 main types; Southern Arrow Squid (Nototodarus sloanii) and Goulds Arrow Squid (Nototodarus gouldi). Seaweek 2006 Photo by Kerry Perkins

  8. Capture locations for squid North Island West Coast Canterbury Otago A Catlins P South Snares N M H G E C South Island J O F Q B D L I K R Seaweek 2006

  9. Age • Squid can be aged using their ear bones (called statoliths). • They have rings in them…like a tree. Seaweek 2006

  10. The statolith was mounted on a microscope slide, ground on wet carborundum paper and polished with 0.05µm Alumina on felt • 281 statoliths were polished (139 male and 142 female) Photomicrograph by Jean McKinnon Seaweek 2006

  11. Lines were counted by using a camera lucida to project the image onto paper which could then be traced. Typical Camera Lucida drawing of a statolith (scale bar = 0.1mm) Seaweek 2006

  12. Squid ranged in age from 29 days to 206 days old. • There was increase in size, (both length and weight) with increasing age. • The data suggested that male and female squid grow differently. • At the same age females are longer and heavier than males, but males are slightly more mature. Seaweek 2006

  13. Other aging? • The gladius or pen is what remains of the mollusc shell. • The increments were counted using a dissection microscope with an adjustable fibre optic light source. Seaweek 2006

  14. Increments Central rib Lateral plate Lateral rib Photomicrograph by Jean McKinnon Seaweek 2006

  15. The counts were very similar to those of the statolith from the same animal. male female r2=0.980 r2=0.997 Statolith versus gladius increment counts Seaweek 2006

  16. The growth curves showed a period of slow growth ranging from 20 to 70 days long. • This pattern could not be attributed to location or hatch season. • Gender appears to be an important factor in the growth rate of the squid. • Female squid show growth curves with only a short period of slow growth, male squid have a longer period of slow growth. Seaweek 2006

  17. Female growth curve • Curves are from squid from the same location, with similar hatch seasons and caught at the same time. Gladius increment growth (mm) Male growth curve Gladius increment number Seaweek 2006

  18. Diet. • What do squid eat??? • Squid are typically predators. • To investigate the diet of the Southern Arrow Squid the stomachs were removed and their contents were examined. • Contents were divided into fish, crustacean, cephalopod remains and “other”. • Any fish otoliths (earbones), squid/octopus beaks and crustacean eye lenses found were kept. Seaweek 2006

  19. Fish prey Crustacean Prey Squid/Octopus prey Seaweek 2006

  20. Fish Prey Species of N. sloanii • Sprat • Silverside • Deep Sea Smelt • Pearlside • Four types of Lanternfish • Red Cod • Hoki • Javelinfish • Seahorse/pipefish • Warehou Seaweek 2006

  21. Other Prey of N. sloanii Cephalopods • Southern Arrow Squid • Goulds Arrow Squid Crustaceans • Krill • Red whale feed “Other” • Bivalves • Crab larvae • Snail Seaweek 2006

  22. Parasites?? • Less than one percent of stomachs examined contained parasites. • These were mainly worms (Anisakis simplex) . Seaweek 2006

  23. The exception to this was the small sample of squid collected from the South Snares Shelf where 88.89% of squid examined contained between 20 and 130 Anisakis simplex worms and 100% contained an as yet unidentified parasite. Seaweek 2006

  24. Why Study Squid? • They are an important component of the marine environment. Both as prey and predator. • They are an important fishery species about which we have only basic information. • There are a huge variety of them ranging from the tiny pygmy squid (3cm long) to the colossal squid (16m + ?????). Seaweek 2006

  25. We are Mythtaken! Most squid do not fit into the ship sinking, submarine eating category! They are instead short lived, fast moving molluscs! Seaweek 2006

  26. Acknowledgements Supervisors/Thesis readers! Dr George Jackson, Dr Philip Mladenov Assoc. Prof. Mike Barker Squid Collectors Sea Resources Ltd., Wellington Master and Crew F. V. Fuji Maru 63 Dr Steve O’Shea , AUT Master and Crew R.V. Kaharoa Sandford South Island Ltd Otakou Fisheries Ltd Mr Peter Fullerton, Sea Lord Co. Ltd Master and Crew F.V. Meridien General John and Kathryn McKinnon Staff and Students of the Department of Marine Science and Portobello Marine Laboratory, Especially, Kerry Perkins, Bev Dickson, Karen Bonney and Daryl Coup Seaweek 2006

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