Abalone and its impact

Discussion in 'Diving, Collecting and Environmental Discussions' started by Kanga, 6 Apr 2008.

  1. Kanga

    Kanga Retired Moderator MASA Contributor

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    So I have been wondering what impact will the extinction of abalone have on our oceans. I understand that my children will never see an Abalone in that case etc and any species we lose will always be a great loss, but after some searching on the net I cant find what ecological impact the extinction of abalone will have.

    So people please enlighten me:thumbup:
     
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  3. Warr7207

    Warr7207

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    Don't know about it being extinct. When I was in China, you could buy it at every restaurant.

    I very popular dish.
     
  4. Kanga

    Kanga Thread Starter Retired Moderator MASA Contributor

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    Yip, it apparently err puts lead in ye olde pencil:p

    But that is the main reason it might end up being extinct is the fact that it is so popular in Japan and China
     
  5. Warr7207

    Warr7207

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    Interesting majority of the abalone is locally cultivated, but i saw a shop advertising RSA Abalone at 100x the normal price, this is the illegal stuff.
     
  6. 459b

    459b Moderator MASA Contributor

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    Abalone farming is a HUGE industry. Most of the abalone for sale will come from commercial farms, even SA has a thriving industry, but due to the ban of abalone sales in SA, all of the abalone we produce is exported. Because of the high price, esp on the black market, abalone poaching is out of control...its not uncommon for abalone farms to be robbed at gunpoint!

    as with any other animal, removing abalone will have an impact on the ecosystem. In the heavily poached areas around Hermanus, where abalone are basically extinct, there has been an increase in the number of sea urchins. Scientists arent sure if this is linked to the dissappearence of abalone. You dont always see the impact immediatly. With our general lack of understanding of the ocean, we will just have to wait and see what the final outcome is.
     
  7. Kanga

    Kanga Thread Starter Retired Moderator MASA Contributor

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    Sheesh armed Abalone robberies, scary stuff.

    I hear you, but I was wandering if there was any direct impact like , no abalone, more algae = less fish = more dead microorganisms etc

    However the idea of a long term imbalance isnt any less scary when you think about it
     
  8. 459b

    459b Moderator MASA Contributor

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    If you have time read this: http://www.environment.gov.au/coasts/fisheries/vic/abalone/pubs/abalone.pdf
    Submission to Environment Australia:
    Assessment of the Victorian Abalone Fishery against Guidelines for the Ecologically Sustainable Management of Fisheries April 2001

    (Its a rather long and boring article so i just included the stuff you are interested in. I know its from Australia, but it should be similar on our coasts)

    1. Impacts on ecological communities
    The main direct impact of the Victorian abalone fishery on ecological communities is
    the removal of 4–7 million abalone annually. No other organisms are removed and
    most competition between abalone and other organisms is for space. It is probable that
    the removal of large numbers of abalone is at least partially compensated by density
    dependent effects on growth and survivorship, however the scientific evidence to
    support this area of theory is scant and equivocal.
    During annual fishery independent surveys, quantitative estimates of abundance of
    prevalent organisms other than abalone are undertaken. For vegetation these include
    cover abundance of major macroalgal divisions, kelp canopy and crustose coralline
    algae. Transect counts of urchins, sea stars, turban snails, and semi-quantitative
    estimates of other invertebrates are also made during these surveys. No counts of reef
    fishes are made, however fish counts are to be included in surveys of unfished MPAs.
    One consequence of excessive stock depletion at a localised scale is the need for
    management intervention aimed at restoration. One restorative option is to translocate
    mature broodstock from nearby populations where abalone remain abundant. This
    raises an issue about potential impacts on genetic diversity within the depleted stock.
    Genetic effects from translocated and outplanted abalone reared in hatcheries have
    been reviewed by Benzie (1996) for South Australia and then extended to Victoria by
    Fleming (1997). The latter forms the basis for the policy on sea ranching that is
    included in the Draft Management Plan.

    Benzie (1996) concluded that any genetic shifts caused by additions of abalone from
    elsewhere would only be maintained whilst the additions continued and that
    permanent changes were improbable. In recommending a strategy for Victoria,
    Fleming (1997) considered the paradox between the large neighbourhood size of
    about 500 km coastline for blacklip abalone and the significant heterogeneity at a
    localised scale of several kilometres identified from the work of Brown (1991) and
    Brown and Murray (1992). The most likely explanation is that whilst gene flow is
    high over evolutionary time scales, inter-annual dispersal of larvae is localised to
    create a distance by isolation genetic structure for blacklip abalone populations.
    Consequently, the metapopulation scale referred to in the Draft Management Plan
    represents a conservative approach to protecting the genetic integrity of Victorian
    abalone wildstocks.
    Parallel concerns about the spread of disease from hatcheries are speculative. An
    endemic disease that thrives under hatchery conditions is likely to revert to low levels
    of infection in the unlikely event it is transferred back into the natural environment.
    Addition of abalone in accordance with the ranching policy poses negligible risk to
    the ecosystem.

    2. Impacts on food webs
    Abalone are one of several dominant benthic herbivore groups in their communities.
    Others include sea urchins and turban snails. However, abalone tend to feed
    predominantly on drift algae rather than graze attached plants, reducing their direct
    competition with other grazing herbivores. Evidence of urchin barrens in Victoria is
    realtively uncommon and confined to Eastern Zone in habitats whereCentrostephanus rodgersii is the dominant urchin species. Barrens habitat is
    characterised by substantial changes in macroalagal assemblages towards
    compositions that are unfavourable to abalone (Andrew and Underwood 1992).
    Heliocidaris erythrogramma is the main urchin species west of Mallacoota and does
    not appear to have the same profound influence that C. rodgersii has on abalone
    communities,.
    Abalone are also prey for a range of reef fishes, particularly wrasses, morwong, rays
    and heterodontid sharks. Other significant predators include sea stars, decapod
    crustaceans and shell-drilling gastropods (Shepherd and Breen 1992). Predator-prey
    interactions depend substantially on the relative size of the abalone to the predator.
    There is likely to be considerable functional redundancy because not all these groups
    are present within every abalone habitat. There is no known top chain predator in
    Victoria that depends solely on abalone for food and it is reasonable to surmise that
    the trophic effects of removing large numbers of abalone from the ecosystem are
    likely to be diffuse. More research is needed to examine the effects of reducing
    abalone populations on energy and nutrient flows within their ecosystems and the
    effects on organisms that may depend on the presence of abalone.

    3. Impacts on the physical environment
    Physical habitat
    Abalone harvesting involves the direct removal of abalone from the substrate. This
    means there is no physical damage to the substrate that can be ascribed to the fishing
    activity. Abalone fishing operations take place from relatively small runabout boats
    (Gorfine and Dixon in-press). As with any small boating activity, there is some
    potential for anchor damage to the substrate and benthic organisms, however in
    temperate rocky reef systems this is negligible in terms of the ecosystem as a whole.
    Water quality
    The only obvious risk to water quality is pollution from spillage of fuel and oil from
    boats and hookah compressors. However the limited number of commercial boats,
    and the volumes involved relative to the volume of seawater, mean that any impacts
    would be isolated and of limited consequence to the ecosystem.

    Hope it helps!!!
     
  9. jacquesb

    jacquesb Retired Moderator

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    Something else I would like to add as well -

    Look at the natural cycle of things:
    Abalone eats something, right? And Abalone feeds something, right?
    So - if I may deduce the following:
    - less abalone, the "food" that abalone consumes would multiply, and become too much - causing a natural imbalance
    - AND: whatever eats abalone (fish? rays? sharks perhaps? - I dunno - add to the list), will now have too little to eat, and what happens? either the animals start eating some other food-source, which would not normally be their food of choice, perhaps causing an in-balance here, OR, they might starve to death, right?

    Please correct me if my thoughts are in the wrong direction....
     
  10. 459b

    459b Moderator MASA Contributor

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    your thinking is correct.
    Abalone are rather difficult to get off the rocks and i dont think any species feeds exclusively on abalone, esp adult abalone. I know the sucker fish feeds on juvenile abalone, but if also eats anything it can fit in its mouth. So i dont think removing abalone will have to much effect on things that eat it.
    As for abalone food becoming too abundant and choking other organisms... abalone feed mainly of kelp fronds or other macro algae that drifts by. Kelp is extremly fast growing and regenerates very quickly (think how much kelp you see washed up on the beach everyday). I dont think any population of abalone effects the abundance, or absence, of kelp.
     
  11. jacquesb

    jacquesb Retired Moderator

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    Hi 459b - thanks for the explanation - awesome!
     
  12. 459b

    459b Moderator MASA Contributor

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    Did a bit more reseasrch. Scientists did some work on the removal of abalone in Tasmania. They removed all the abalone from an area and noted a change in no. invertebrates and the matrix of filamentous algae. They noted a change from "pink rock" ( top picture: rock covered in corraline algae) to "brown rock" ( bottom picture: rock covered predominantly in filamentous algae and sediment). Pink rock typically supports large abalone populations. They cannot conlude whether the removal of the sea urchins will result in the environment returning to pink rock or brown rock.

    [​IMG]


    [​IMG]

    Unfortuanatly i cant access the entire publication. Still cant find anything relating to South Africa. Will keep looking.
     
  13. jacquesb

    jacquesb Retired Moderator

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    Cool! Thanks 459b - so - there is SOME logic to my comment then.... That's what we talk about.... impacts of removing abalone from the equation....
     
  14. 459b

    459b Moderator MASA Contributor

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    i wish they had given the time scale of the experiment. Not sure how long it took for the rock to turn "brown". So still no answer to the immediate impact of removing abalone.
     
  15. Kanga

    Kanga Thread Starter Retired Moderator MASA Contributor

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    459. jacques, thanks guys thats exactly what I wanted to know, any idea what would the secondary effects there would be
     
  16. 459b

    459b Moderator MASA Contributor

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    not sure if those are the secondary effects. The article never gave a time scale and was very limited to what organisms they mentioned. I would have liked to have known what happened to the fish populations etc, cause all that filamentous algae would definatly be good food and hiding places for small fish.
    I tried to find more info on the situation in SA, but it seems all the funding for abalone poaching is going to studying the socio-economic impact of poaching. Turns out poached abalone aren't sold for cash, but rather swopped for the raw ingredients needed to make drugs.
     
  17. Kanga

    Kanga Thread Starter Retired Moderator MASA Contributor

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    WOW no wonder you here so many stories RE how rough these guys are.

    It does seem however that long term effects could cause a huge swing in the ecological balance

    459, thanks again for your input:thumbup:
     
  18. 459b

    459b Moderator MASA Contributor

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    Just came across this article by Steneck et al. (2002). Kelp forest ecosystems: biodiversity, stability, resilience and future.
    They never mentioned abalone but rather looked at the entire kelp ecosystem in California. They observed that over fishing increased the number of sea urchins (as jacquesb mentioned, remove predator = more prey etc), ultimately resulting in deforestation. Once all the fish had been removed, together with an increase in the demand for sea urchins, fishing shifted from targeting apex predators to sea urchins. Removal of sea urchins did result in the re-establishment of the kelp forests, but for the first time the forests were devoid of a vertebrate apex predator. Instead, large predatory crabs moved in and became the new apex predator in the system. Similar shifts from fish to crab dominance have been seen in the UK and Japan.
     
  19. jacquesb

    jacquesb Retired Moderator

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    Very interesting info 459b! Thanks for that! Just goes to show... I wish we had more people like you and LappiesReef and Crispin on our forum. You guys need to share a LOT more info with us, that we can all collectively LEARN about our oceans! ;-)

    The more knowledge - the better we will be able to look after our oceans!
     
  20. 459b

    459b Moderator MASA Contributor

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    no problem. glad i could help
     
  21. sihaya

    sihaya

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    I think they're cool. I have 2 of one of the smaller species in my system.
     
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