New Zealand kelp forests under threat as total allowable catch limits announced

By Rebecca McLeod 24/09/2010 30

I am still reeling from an announcement made yesterday by the Minster of Fisheries and Aquaculture Phil Heatley regarding the setting of the total allowable “catch” for giant kelp (Macrocystis pyrifera). I thought I might try and calm down a little before I wrote this post, but the 20 or so emails that greeted me this morning from marine ecologists throughout the country made me realise that I am definitely not alone in feeling completely frustrated and disillusioned about the process of consultation and setting of catch limits for some of the species managed under the Quota Management System (QMS).

Just a little bit of background first. Last year the Ministry of Fisheries, following a period of consultation, entered giant kelp into the QMS (I wrote about this at the time: “One step closer to harvesting kelp“). It was a tough one for those concerned about the important ecological role that this species plays (perhaps most obviously in providing a home and food source for countless marine animals) – if the species wasn’t entered into the QMS, expiration of a harvesting moratorium would mean that there were no controls on the amount of kelp that could be literally mowed from kelp forests around the South Island. A second round of consultation followed earlier this year, where the Ministry produced three options for total allowable catch for the management area that extends from a point near Kaikoura all the way down to Slope Point at the southern most tip of the South Island. These options were 1) 375.8 tonnes, 2) 40 tonnes, and 3) 17 tonnes.

Given the paucity of scientific knowledge about the effects of removing the canopy of kelp forests on the species that rely on this habitat and food source, myself and a great number of marine scientists argued that a cautious approach should be taken and thus the catch limits set very low – at least until our scientific understanding improves. If you are interested in the current state of knowledge and concerns that many scientists have, I wrote an extensive post on this last year – “Is it wise to mow our kelp forests?

Anyway, moving right along, I was more than a little shall we say… surprised… to read the Minister’s announcement yesterday that the total allowable catch for the east coast of the South Island had been set at… wait for it…. 1,238 tonnes!!! TA DAAAAA!!!! But hang on a minute, wasn’t the largest option put forward by his own advisors 375.8 tonnes? Well yes. But, well, what would they know? Now I obviously don’t have a good understanding of how this process works. What is the point of asking for submissions about a range of catch options if you are only going to dream up a completely new figure? How can this be legal?!

But, rest easy my friends, the Ministry of Fisheries Chief Executive Wayne McNee said ’The Minister was very mindful of the important role bladder kelp plays in the ecosystem and has imposed conservative controls on harvest to make sure this role is not compromised.’ Oh PHEW! Here I was thinking that it must all be about money.

It takes a lot of time and research to write a submission that is based on current scientific knowledge. I personally feel like the effort that my colleagues and I put into this process was a complete and utter waste of time. If anyone can enlighten me as to how this ‘game’ works, I would really appreciate it. But perhaps more importantly, we need to start seriously thinking about ways to protect our local kelp forests – it is not only scientists that should be worried about the imminent threat that they now face. Recreational and commercial fishers, divers, coastal dwellers: this is very much your problem too.

Grrr grrr grrrr, over and out.

30 Responses to “New Zealand kelp forests under threat as total allowable catch limits announced”

  • Unbelievable – seems like a bad joke. Definitely worth pursuing some answers from the Minister on how this decision was made.

  • Rebecca states that there is a pausity of information regarding the effects of removing the canopy of giant kelp forests. I would claim that there is a pausity in our basic knowledge of how these ecosystems function full stop. We no relatively nothing regarding species interactions, both between Macrocystis and other macroalgae and between Macrocystis and the herbivores/detritivores that rely on it for food, or how Macrocystis populations are influenced by environmental factors. The removal of Macrocystis could have no ecoclogical effect, though this is very unlikely. I fear that the removal of kelp biomass could have implications for local fisheries that rely on kelp. We have no knowledge of what the long-term implications of this might be for near-shore rocky reef ecosystems that are laready heavily influenced by human acitivies. – It’s not like near-shore rocky reefs in NZ are being influenced by any other anthropogenic stressors already, so why not remove most of the bottom of their food-chains?

  • The crux of the management issue is that MFish is using a fisheries model that involves developing a ‘fishery’ up to MSY. Using this model, the more that is discovered about the biomass that is out there, the more presure there will be on them to allow commercial interests to access it. I am not sure how the important role of Macrocystis biomass and the detrital food it provides on a large scale for nearshore marine foodwebs can be recognised and protected under QM.

  • I think they listened to submissions “The majority of submissions support QMS management but within the context of TACs set at zero for each stock. The support for this approach reflects an overwhelming desire to prohibit the harvest of this seaweed within FMAs 3 and 4, as well as nationally” then disregarded them.

    Perhaps opposition to harvesting from the Department of Conservation (Otago Conservancy), East Otago Taiapure Management Committee, Bill Hartley, Hokianga Accord/Option4, Kaikoura Boating Club, Kati Huirapa Runaka ki Puketeraki, Dr Wendy Nelson, New Zealand Conservation Authority, New Zealand Marine Sciences Society, New Zealand Recreational Fishing Council, New Zealand Underwater, Ngä Motu Marine Reserve Society Inc, Otago Conservation Board, Royal Forest and Bird Protection Society of New Zealand Inc., Colin Ryder, Kuini Scott, , Seaweed Association of New Zealand Inc, Te Korowai o Te Tai o Marokura, Te Runanga o Ngai Tahu, University of Auckland (Leigh Marine Laboratory, and Wellington Recreational Marine Fishers’ Association (Inc) shouldn’t be seen as credible?

    Limited support from a few industry players (New Zealand Rock Lobster Industry Council, New Zealand Seafood Industry Council Ltd, PAUAMAC 4 Industry Associated Incorporated) for careful management under the QMS and an extensive submission the major proponent of the kelp fishery on TAC (Sea Right Investments) led to a tripling of TAC, hmmm.

    The management measures provided to protect this habitat forming species are taken directly from the submission of Sea Right Investments and are entirely insufficient to sustainably manage Macrocystis across the huge expanse of the management areas.

    It’s not like kelp forests support industries (e.g. crayfish, paua and finfish fisheries) that provide many millions of dollars of export dollars to the country, without even going into the huge number of other services this species provides. Lets make low value fertiliser out of it, stick it on the land. You can’t fault that logic.

    The obvious lesson is to give up science and become a politician if you want to have any say on the future of our fisheries.

    Learn more bout this baffling decision at:

  • Frustrating indeed! No doubt we will see an announcement in the coming days that the government is also going to spontaneously increase the funding available to manage this fishery by between 7200% and 230%. No… wait… Bugger.

  • Of interest perhaps: Shane Geange at Vic Uni was recently awarded a Postdoctoral Fellowship to study the ecological effects of commercially harvesting New Zealand bladder kelp.

  • Wow! looks like the ministry of fisheries consultation processes just a waste of time! Why did we bother? Pandering to a single stakeholder who has the most to gain. What is the point of a process to gauge opinion of stakeholders and give options to set a TAC when you then completely disregard all submissions except those of the person who has the most to gain and double the maximal TAC option….. Totally unbelievable! Where is this historical data they speak of of the “biomass of kelp forests”? Thankyou Hon Phil Heatley and the team at MFISH you have made me proud to live in a country such as ours and to pursue a career in business then maybe I might have a chance of being heard.

  • Well done on raising this issue Becs! It’s an inditement on the way MFish “manage” (ha ha ha haaaa!) our fisheries. The QMS bases the allocation of quota not on robust scientific information but on historical catch rates and poorly designed models that are not based on the biology of the organism being fished. Conservative, sustainable fisheries management is a concept MFish does not seem to understand! I think that they had their mind made up about this fishery before submissions were even sent out let alone received… The decision seems to benefit one sector “Sea Right Investments” over the majority of people who have some connection with this important ecosystem engineer!

  • Thanks for all the additional information everyone. I’m getting an awful sinking feeling here. Why the hell is all this not being concentrated on Undaria?

  • Truly staggering.
    And now for the unintended consequences…
    e.g. Rapidly accelerating coastal erosion at south Wairarapa has been directly attributed to kelp bed loss.
    That Wairarapa kelp loss is attributable to nitrate runoff is immaterial. It highlights that increasing the risk of even localised kelp system failure has potentially severe (and costly) impact.

  • I suggest you OIA Heatley’s advice on the setting of that figure. He’s made claims about it being the result of a conservative calculation; so get that calculation and see if it stands up to scrutiny. If not, publicly trash it.

  • Yup that OIA request has gone in. Rather a few MFish media statements bluffing the same line recently.

    Mikey Mike.
    Keen to find out more about the Wairarapa situation. Anything documented you could pass onto me?

  • Leave your comment here…

    Dr Pamela Mace, Chief Scientist, Ministry of Fisheries:

    International examples show that bladder kelp is economically valuable and, if managed properly, harvesting can result in little environmental impact.

    The total allowable catches (TACs) in the initial position paper were based on the best information available to the Ministry at the time.

    The higher TACs in the final advice paper (FAP) reflect new information on the amount of seaweed (biomass) provided through the submission process.

    Submitters provided additional information, particularly from a research paper that gave biomass estimates of bladder kelp in Pleasant River (Otago) off the south east coast of the South Island, and also satellite imagery off the Chatham Islands coastline.

    Aerial photographs provided by Environment Canterbury were also obtained of bladder kelp beds off Pitt Island, Waitangi West, Owenga and Okawa Point in the Chatham Islands.

    The new information was reviewed by the Ministry’s Science team and was used to revise the biomass information available and to inform yield calculations.

    The adjusted biomass estimates used are still conservative because the bladder kelp resource in each quota management area (QMA) is distributed across areas outside those used to estimate biomass.

    o For the south east coast of the South Island (KBB3G) the combined total survey biomass came from only two areas, Akaroa Harbour and Pleasant River.
    o For the Chatham Islands (KBB4G) the area coverage from the aerial images analysed was reduced by between 25 percent and 50 percent to minimise the risk of overestimating biomass and subsequent yield when calculating sustainable yields.
    In each QMA the yield of bladder kelp able to be sustainably harvested was determined by calculating sustainable yields based on the biomass estimate. More information on these calculations is available in the FAP which is available at:

    Other management measures have also been adopted to support sustainable fishing activity and minimise the risks of localised depletion.

    A maximum cutting depth of 1.2 metres from the sea surface will enable individual plants to continue to grow and reproduce.

    Overseas studies show that kelp are very productive and grow at high rates, so it is likely that they will be able quickly to replenish the amount harvested.

    Harvesting of kelp will also be monitored on fine spatial scales to allow for adaptive and responsive management approaches should there be adverse effects from harvesting.

  • Great to read all the comments! Thanks for your input – a very worthwhile discussion I think. I am also very pleased to get feedback from MFish (Pamela Mace, above), particularly the clarification on the setting of the total allowable catch (TAC) for KBB3G (the South Island).

    Thanks to a few tip offs above, I think I now have a clearer understanding of how the TAC for KBB3G came to be set so much higher than that proposed in the consultation document. This is partly explained in Pamela Mace’s comment above, but I would like to discuss this a little more.

    As I explained in the original post, the initial position paper listed 3 options for TAC, with the highest being 375.8 tonnes. Submissions were then received by MFish, and a few (from what we could call “commercially-interested parties”) drew the attention of MFish to some estimates of kelp biomass/standing stock. These estimates were then used by MFish to calculate two additional TAC options – 1864.8 tonnes, and 1236.8 tonnes that were put to the Minister in the final advice paper. As I understand it (and please correct me if I’m wrong Pamela), these TAC options were calculated from models of maximum sustainable yield used overseas (e.g. the Californian kelp fishery). Interesting to hear your concerns about these models Jim. What has frustrated the scientists I have talked to is these revised TAC options were never put back out for public consultation.

    Had they been, my response would have been: a) we know that there is huge variability in growth rates of this species both spatially and temporally, and these differences have not been adequately studied to date, and b) this is NZ, not California – there are some very large differences in kelp forests between these two locations and it is therefore not scientifically robust to base estimates for sustainable yields on the Californian forests (summarised below).

    Californian kelp forests:
    1. Very large in extent – individual patches up to 10 km2 (Dayton et al. 1998)
    2. Latitude 33°N – high light, kelp growth not limited by light (Zimmerman and Kremer 1986, Kain 1989)
    3. Relatively consistent growth year round and growth only slows in summer due to low seawater nitrogen (e.g. Zimmerman and Kremer 1986)

    South Island kelp forests:
    1. Small and discrete – individual patches typically <100 m2. Large beds are only found along the North Otago coast and are <1km2 (Fyfe et al. 1999)
    2. Latitude 41-47°S – relatively low light, kelp growth limited by light (Kain 1989, Hepburn et al. 2005 and 2007)).
    3. High variability in growth rates among sites due to light, nutrients and water motion. Respond to seasonal fluctuations in light with maximal growth during spring (Brown et al. 1997, Hepburn et al. 2005 and 2007)

    There has also been a bit of discussion around the additional management measures that have been adopted to "reduce the potential adverse effects from harvesting on localised
    areas and associated and/or dependent species, and enable greater utilisation". These measures include a) limiting the maximum cutting depth to 1.2 m, b) limiting the width of harvesting strips to a maximum of 5 m, and c) limiting harvesting of each bed to 2 times per year and to 50% of each bed.

    My concerns about these measures? a) At least 90% of the biomass is in the top 1.2 m (the canopy), b) there is no mention of how far apart these strips have to be from each other – could they be spaced 0 m apart?!, and c) unlike California, Macrocystis growth in NZ is highly seasonal – but there is no regulation on the timing of these two harvests. If there is more than one operator, what is to stop the 2nd coming along and harvesting the remaining 50% (well half of that I suppose), and the bed being subjected to more than 2 harvesting events in a year? I am not at all convinced that these additional measures will prevent serial depletion of our kelp forests.

    Finally, it is good to read that "Harvesting of kelp will also be monitored on fine spatial scales to allow for adaptive and responsive management approaches should there be adverse effects from harvesting". But, what exactly is going to be monitored? The direct effects on Macrocystis biomass, or the potential indirect effects of harvesting on species that live in and around the forests and feed upon the living or detached kelp? It is these indirect effects that are of particular concern, and they will be inherently difficult to monitor.

    Brown, M. T., M. A. Nyman, J. A. Keogh, and N. K. M. Chin. 1997. Seasonal growth of the giant kelp Macrocystis pyrifera in New Zealand. Marine Biology 129:417-424.

    Dayton, P.K., Tegner, M.J., Edwards, P.B., and K.L. Riser (1998) Sliding baselines, ghosts, and reduced expectations in kelp forest communities. Ecological Applications 8(2): 309-322

    Hepburn C.D and C.L Hurd (2005). Conditional mutualism between the giant kelp Macrocystis pyrifera and colonial epifauna. Marine Ecology Progress Series 302: 37-48.

    Hepburn C.D, J.D Holborow, S.R Wing, R.D Frew, and C.L Hurd (2007). Exposure to waves enhances the growth rate and nitrogen status of the giant kelp Macrocystis pyrifera. Marine Ecology Progress Series 339: 99-108

    Kain, J.M. (1989) The seasons in the subtidal. British Phycological Journal 24:v203-215.

    Zimmerman, R. C., and J. N. Kremer. (1986) In situ growth and chemical composition of the giant kelp, Macrocystis pyrifera: response to temporal changes in ambient nutrient availability. Marine Ecology Progress Series 27:277-285.

  • Leave your comment here…

    Dr Pamela Mace, Chief Scientist, Ministry of Fisheries:

    First, I would like to correct or clarify some of the statements made by Rebecca McLeod in her most recent blog on this subject:

    1. The total allowable catch (TAC) options were calculated using formulations developed in New Zealand in 1988, and periodically updated, not “models of maximum sustainable yield used overseas (e.g. for the California kelp fishery)” – see the Introduction in Ministry of Fisheries (2010). In fact, California does not set TACs to control the amount of kelp harvested; rather, harvesters lease a bed and control harvest rates themselves unless removals are deemed excessive.
    2. Growth rates of kelp are quite variable in New Zealand. The best available growth data were from Akaroa Harbour (Pirker 2002), and were applied to Akaroa, the Otago coastline and the Chatham Islands. Growth rates of kelp are generally higher in more exposed locations (Graham and Vasquez et al. 2007), such as the Chatham Islands and the Otago coastline. Therefore, using data from Akaroa Harbour may underestimate sustainable harvest rates at the other locations.
    3. Rebecca incorrectly states that over 90% of biomass is held within the kelp canopy. Data from New Zealand shows that the maximum biomass in the canopy ranged from 0% to 73% in three locations (two in Akaroa Harbour and one in the Marlborough Sounds) monitored over three years (Pirker 2002). A figure of 50% was used by Ministry of Fisheries scientists to calculate biomass levels.

    We believe the biomass levels on which TAC calculations were based are conservative because:
    • they assume a conservative growth rate for the majority of the beds (based on observed rates for Akaroa Harbour), and assume a conservative scaling factor to convert area to canopy biomass in the Chathams Islands; and
    • other kelp beds from the South Island coast were omitted from the calculations because no biomass estimates were available.

    Harvesting only the top 1.2 metres of the kelp should equate to no more than 50% of the biomass of the cropped area, and to less than this for the bed as a whole. This should retain much of the ecological role of the kelp beds, but the Ministry is keen to see further work to verify this. One such example is a FRST-funded project entitled: “Evaluating the ecological effects of commercially harvesting bladder kelp” that is being conducted by a postdoctoral fellow at Victoria University, with input from the Ministry.


    Graham, M, J Vasquez, et al. (2007). Global ecology of the giant kelp Macrocystis: from ecotypes to ecosystems. Oceanography and Marine Biology: An annual review. 45: 39-88.
    Ministry of Fisheries (2010). Report from the Fisheries Assessment Plenary, May 2010: stock assessments and yield estimates. Wellington, New Zealand Ministry of Fisheries: 1158 p.
    Pirker, J (2002). Demography, production, biomass and effects of harvesting giant kelp, Macrocystis pyrifera (Linnaeus), in southern New Zealand. University of Canterbury. PhD Thesis. 244 p.

  • Dear Dr Pamela Mace, Chief Scientist, Ministry of Fisheries:
    I would like to comment on some of the statements made by you!

    you say “Rebecca incorrectly states that over 90% of biomass is held within the kelp canopy. Data from New Zealand shows that the maximum biomass in the canopy ranged from 0% to 73% in three locations (two in Akaroa Harbour and one in the Marlborough Sounds)”.

    Ok that may be true for Akaroa Harbour and the Marlborough Sounds populations but what relevance does that have to the open coast kelp beds…? where there can be 90 % of the biomass in the top 1.2 m (pers. obs. D Richards 6 years of diving in kelp beds along the Otago coast). Will the harvest of this species be conducted at high or low tide? This could considerably affect the amount of biomass that is included in the top 1.2m of the water column (at low tide there will be far more biomass on the surface). The depth of the bed will also play a part in how much biomass is removed e.g. a bed at a depth of 12m vs 5m….10% of available forest height vs 24%, was this taken into account?

    You also state “Harvesting only the top 1.2 metres of the kelp should equate to no more than 50% of the biomass of the cropped area, and to less than this for the bed as a whole. This should retain much of the ecological role of the kelp beds”

    This should retain much of the ecological role of the kelp beds…. how do you know this? I suggest you study this question first BEFORE you allow harvesting, not the usual approach of verifying after the fact!

  • This fisheries model’s assume that there is “spare” dissolved organic matter. Current DOM is fully utilised within the ecological system.
    If the fishery is developed up to MSY this will have a direct and substantial impact on the DOM available in the nearshore.

    How are changes in DOM, and the consequences of this, going to be measured and accounted for? This is an important aspect of sustainable management that MFish has failed to explain or manage within its QM model, and its tripling of TACC on the basis of an adhoc discovery of the additional biomass confirms the lack of integrity of the model.

  • It appears that my research based on the Pleasant River kelp beds in the late 1990s was used to justify tripling the TACC.

    Firstly, I would like to point out the paper, from which the extent and biomass estimates for the Pleasant River beds have been conveniently adopted, highlighted how dramatically the the extent and biomass changed over time. The paper concludes ‘a long-term baseline study of the dynamics of non-harvested Macrocystis beds will be necessary to assess any impacts that harvesting has on production cycles’.

    I suggest that, if the Ministry is serious about taking a cautious approach, they might consider the biology of the beds and the role that they play in the local ecology, rather than equating the known occurence of biomass with an assumption that it won’t hurt to take a proportion of it. A biomass estimate from 10 years ago used (out of context) to justify increasing the TACC so dramatically (without further investigation) is, in my opinion not a convincing demonstration of caution.

    Harvesting is likely to alter the structure and cycles within these beds because the removal of the Macrocystis by storm waves is important for synchronising cycles. Harvesting will reduce the surface drag, prolonging the occurence of old plants at a cost to the recruitment of younger more vigorously growing individuals.

    Also, the invasive seaweed, Undaria, has just arrived in this area and could possible compete for reef space if harvesting changes the sub-canopy light dynamics.

    More study is needed before subjecting these beds to the 800+tonne harvest proposed.

  • Thank you MFish (Pamela Mace) for clarifying the biomass distribution figures. I have had a closer look at the Pirker thesis (2002) and found the seasonality in the vertical distribution of Macrocystis biomass to be very interesting. Pirker defined the canopy as the top 1 m (vs. 1.2 m in the fishery models), and measured the proportion of total kelp biomass occurring in this uppermost meter. He found that within the same bed, the biomass in the canopy was very low in the summer months (<<50%), but increased to above 50% in the winter months. I can't imagine that it would be economically viable to harvest in the summer months when such a small proportion of the biomass is within cutting reach, and so assume that harvesting pressure would be highest in the cooler months when biomass in the top meter is often in excess of 50%. But, when you take a step back and consider this issue from a wider ecological perspective, these numbers become somewhat irrelevant.

    We still don't know what proportion of the biomass can be removed before there are wider ecological implications. We can put any number we like into harvesting models, but until we know the answer to this question, well, it all just seems rather arbitrary. Such a question will by no means be any easy one to answer – particularly when one thinks about the diversity of species that use kelp as a food source and habitat, the natural variability inherent in these communities, and the distance over which Macrocystis sustains life (kelp detritus acting as a major food source to beach and deep sea canyon communities).

    It is great to hear there is some research underway and I wish Shane all the best. If only we could wait to see and assess the outcomes of this research before the mowing begins! Now that would be a cautious/conservative approach!

  • Shane Geange, Victoria University of Wellington

    I found these posts interesting reading, and I thought it might be beneficial just to let people know that I am beginning a 3 yr post-doc at Victoria University this month (Oct 2010) that will evaluate the ecological effects of commercially harvesting bladder kelp.

    Initially, I am planning to conduct a series of studies that use a Before-After-Control-Impact-Paired-Series (BACIPs) approach to examine the potential effects harvesting has on sub-tidal communities supported by Macrocystis forests. I plan to have study sites in Wellington, Otago and somewhere a little further southern (potentially Stewart Island) to ensure the broad relevance of results.

    One of the things that initially attracted me to this project is that it could, if done properly, yield data that can be used to inform the management of Macrocystis. I have, and will continue to liaise with MFish during the project. However, if anyone else feels that the data from my project could be useful to them, or there are specific questions they think should be addressed by this research (without compromising the integrity of the study, or my loosing control of it), I would like to hear from them.

    Given that I am about to undertake a project examining the ecologically consequences of harvesting Macrocystis, I will, for the sake of objectivity, avoid wading into the middle of a debate concerning TAC’s, except to say that some of the issues raised in this blog (e.g., amount of biomass present in top 1.2 m of water column; variability in growth rates of Macrocystis; density within forests; effects of harvesting on associated fish/invertebrates and undaria) are things I plan to examine (to varying degrees) in this study.

    Anyway, I thought I would let you know that I am out here, and will hopefully have this project up and running in the next few months.

    Cheers, Shane.