Question for Myopsida

Discussion in 'Physiology and Biology' started by Steve O'Shea, Aug 7, 2003.

  1. Steve O'Shea

    Steve O'Shea Colossal Squid Supporter

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    My good fellow, a little bird once told me that they used to trawl for 'small' Patagonian Toothfish in 'surface waters' (small being ~ 1m total length), and that it was only when these 'immature' stocks were depleted that long-lining to ~ 1000/1100 m commenced to catch the big ones (to 2 m length).

    Is there any truth in this statement? If so, is there anywhere that you can refer me to to get some data on this (stats/history)?

    Twould be much appreciated
    :notworth:
    Cheers
    O
     
  2. myopsida

    myopsida Vampyroteuthis Supporter

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    Quite true, Dr O.
    Juvenile toothfish are pelagic and are schooling fishes - at about `65-75 cm length they settle down and become benthic adults. Midwater trawlers target the juvenile schools, bottom longliners target the adults on the seabed. Basically, for obvious reasons, this is why toothfish fisheries last an average of 3-5 years as each new fishing ground is discovered and exploited. Most of the area around South Georgia was well documented 20-25 years ago, one of the reasons why there is so much attention on controlling (?) poaching in the remaining areas in the southern Pacific. There are several studies - I'll dig out the references tomorrow.
     
  3. Steve O'Shea

    Steve O'Shea Colossal Squid Supporter

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    Thanking you anon Myopsida; then it is only fair to express a concern that the diet of such colossal beasts like Mesonychoteuthis is under threat .... and if one follows the food chain a little further, the diet of bull sperm whales.

    What has come of this world?
     
  4. myopsida

    myopsida Vampyroteuthis Supporter

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  5. Steve O'Shea

    Steve O'Shea Colossal Squid Supporter

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    Part of a proposal to do research on sperm whale dietary shifts as a consequence of fishing activity, just FYI (I'm trying to raise money and awareness for a student scholarship)......

    Trawling is the most pervasive of marine activities to depths of 1200 m - a depth to which the sperm whale regularly dives. Many squid and octopus are retained as fisheries bycatch, trawled and discarded dead at sea. As a sperm whale can consume 800-1000 squid per day (Clarke 1980), it follows that any change in either the size-class composition or diversity of cephalopod fauna will be manifested in the diet of the whale. The squid fauna and size-class structure therefore act as environmental barometers, providing an index of environmental health from a whale’s perspective.

    The threat of deep-sea trawling to the diet of the sperm whale is very real. Five species of large-bodied cephalopod are presently considered threatened or endangered in the DOC ‘Threat Classification System” (Hitchmough 2002) - each as a consequence of deep-sea bottom-trawling activity: Cirroctopus hochbergi, Opisthoteuthis mero, O. chathamensis, Octopus kaharoa, and Idioteuthis cordiformis. Other large-bodied squid not listed in this classification, for which concern is here expressed, are: Taningia danae, Taningia sp. nov., Octopoteuthis sp. nov. (giant), Lepidoteuthis grimaldi, Pholidoteuthis boschmai, Architeuthis dux, any of 7 locally occurring species of Histioteuthis, and any of three species of Moroteuthis. Two of the former, Opisthoteuthis mero and Idioteuthis cordiformis, and all of the latter are either a significant part of or component in the diet of sperm whales (Physeter catodon).

    With the apparent decrease in both abundance and diversity of large-bodied cephalopod species in our waters, and the effective collapse of orange roughy stocks (reported from the stomachs of sperm whales by Gaskin & Cawthorn (1967)), it is likely that the diet of toothed whales, particularly sperm whales, has changed already, and worse still, has been forced to change as a direct consequence of deep-sea trawling. If unregulated, the long-term repercussions are devastating.

    REFS:
    Clarke, M.R. 1980: Cephalopoda in the diet of sperm whales of the Southern Hemisphere and their bearing on sperm whale biology. Discovery Reports 37: 1-324.

    Gaskin, D.E. Cawthorn, M.W. 1967. Diet and feeding habits of the sperm whale (Physeter catodon L.) in the Cook Strait region of New Zealand. New Zealand Journal of Marine and Freshwater Research, 1(1[/i]): 156-179.

    Hitchmough, R. (comp.) 2002. New Zealand Threat Classification lists - 2002. (Department of Conservation) Threatened species occasional publication 23: 210pp.
     
  6. myopsida

    myopsida Vampyroteuthis Supporter

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    1992: Antarctic Fish and fisheries, by Karl-Hermann Kock, Cambridge University Press. ISBN 0-521-36250
     
  7. Steve O'Shea

    Steve O'Shea Colossal Squid Supporter

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    When you mention 'mid-water' for the immature toothfish, what sort of depth are you talking.

    I happened to see the video of this 'colossal squid' being hauled aboard the deck of the fishing vessel concerned (the imagery will never make its way to the big screen for a number of reasons .... it is pretty barbaric for one), and the vessel was actually working amongst pack ice.

    How on earth could you trawl in that sort of environment? Are the smaller toothfish found further north/away from the icebergs? Or it just that the imagery I saw was in this sort of environment (and that not all vessels are working amongst the bergs)?

    Thanks for the ref.
    Ta
    O
     
  8. myopsida

    myopsida Vampyroteuthis Supporter

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    Toothfish catches have been reported since the mid 1970s, although some soviet bloc nations were fishing toothfish as early as the 1960s. Initially the effort focussed well north of the pack-ice - ie around South Georgia, Kerguelen etc. Trawling targetted the larger immature fish of `65+cm in depths of 400-600m, both in midwater and 'near bottom'. Longlining was introduced in the 1980s and has encompassed the entire bathymetric range down to 2500m. Biomass and stock estimates are/were unknown, however, the Kerguelen fishery declined every year from first reporting (1984 ca. 6,500 tonnes to ca. 1,000 t in 1990). the estimated Total Allowable Catch for the kerguelen Plateau was less than 1,000t and was exceeded every year. The fishery has since been closed. The South African fishery began in 1998 and collapsed by 2001. The Australian fishery is expected to collapse within 5 years (because of poaching, not mismanagement according to the wizards of oz). There is no fishery in the southern NZ waters as there are no toothfish stocks - whether this is because they were never there or were stripped out before the EEZ was declared in the 1970s is an interesting question.
    Any trawling or longlining would obviously wish to avoid pack ice - the imagery you are seeing simply reflects the lack of fish stocks in more climatically favourable ice-free areas (in summer at least). The good news is that if your squidly beasts can hang in there for another 5-10 years, the collapse of subsidised factory trawling & longline fishing vessel industry after the next oil shock will enable a recovery.
    :boohoo:
     
  9. Steve O'Shea

    Steve O'Shea Colossal Squid Supporter

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    Thanks Myopsida; food for thought, for sure.
    Several letters of mine to MFish, and the SOP have gone unanswered, one for 2 months, one for 2 weeks. Perhaps I've earnt a reputation as an antagonist? Perhaps I'm just impatient.

    I see I have much background reading to do.
    Ta
    O
     
  10. Ogross

    Ogross Pygmy Octopus Registered

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    NGO toothfish report

    :grad:

    Hi

    The lighthouse foundation has financed a good overview report of the
    ("dirty devasting and criminal.....") toothfish industry:

    http://www.lighthouse-foundation.org/lighthouse-foundation.org/eng/explorer/artikel00428eng.html

    Thought it might be interesting....

    Overfishing is the MAIN reason for the decline of the underwater paradise and future thrats of ongoing species compensation.

    Asked, what job he later wants to do, my son (6 yr.) said yesterday:
    Hammerhead shark rider! :idea:

    I hope for him they are still around in 20 yrs.!!!

    Onno
     
  11. Steve O'Shea

    Steve O'Shea Colossal Squid Supporter

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    Thanks very much for that Onno; are you affiliated in some way with the University of Tasmania?
    Kindest
    Steve
     
  12. Ogross

    Ogross Pygmy Octopus Registered

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    tasmanian wolf

    Hi steve
    nope - neve been in tasman yet :(
    but heard its near an architeuthis spot, so a must go one day...
    cheers Onno
     
  13. WhiteKiboko

    WhiteKiboko Colossal Squid Supporter Registered

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  14. Steve O'Shea

    Steve O'Shea Colossal Squid Supporter

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    ..... out of my league now, Myopsida. Have a presentation to give to politicians on the state of this, that and the other, fisheries wise, in ~ 1 months time, on behalf of F & B. More to follow via e- shortly, but can I quiz you on occasion in such matters, as I have already, and turn this thread into a state of affairs on NZ fisheries (cough) conservation?

    To pull this off I'll have to hang up the ceph paper writing for a month-or-so in order to familiarise myself with all the jargon. Shame, because there's so much happening w.r.t. squid right now.
    O
     
  15. myopsida

    myopsida Vampyroteuthis Supporter

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    No problem Steve.
    I wish I could remember who the fisheries manager was who told me some years ago that the orange roughy fishery should be regulated the same way the the mining industry - seemed to sum up the entire management (?) philosophy.
     
  16. o.vulgaris

    o.vulgaris Vampyroteuthis Registered

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    myopsida, you really need to race a skyline gtr some time, are you in the u.s.?
    i don't mind giving you a ride in mine. :)
     
  17. Melissa

    Melissa Larger Pacific Striped Octopus Supporter

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  18. Clem

    Clem Architeuthis Supporter Registered

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    Melissa,

    Thanks for posting that link; I'd read an article about the poachers a few days ago, when the chase was on. Glad to know the resolution. Perhaps the crew will wonder aloud to their interrogators about what manner of animal was responsible for munching "their" toothfish off the longlines.

    :wink:

    Clem
     

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