Report – EV3203 – Ministrial Briefing II

EV 3203

To: Minister for the Environment

From: Stefan Martensson, Conservationist / Political Advisor.

Re: Detection of Declining Trends in Populations of Marine Wildlife in Queensland

Background: The marine mega-fauna tend to be long lived and take long time before reaching sexual maturity. This means that the effects of harvest from a long-lived animal will not be noticeable until the ‘missing generation’ were to take the place of the present generation. Due to this gap it can be 50 years into the future before we see the effects of declining trends in populations of marine wildlife.

Issues: Our marine mega-fauna has been and still are hunted in many parts of the world. Due to whales, dolphins, sharks, turtles and dugongs are all long lived (25 – 70 years, some even longer) they also have a high age at maturity (10-35 years). Due to both direct and in-direct anthropogenic activities like direct hunting and in-direct by trawling a bias towards a take of the largest animals (which are the mature and breeding animals) because it is more economically for fishermen. These human activities has taken big chunks out from the breeding portion of the populations which has resulted in collapses in many populations already, e.g. the humpback whale and the orange roughy.

It has been shown in many studies that to make a harvest from any animal population, growth models can be used to find out how much is a sustainable harvest. The Growth models look at the reproductive rates and mortality schedules e.g. age at sexual maturity, fecundity and reproductive lifespan. Also survival rates from natural and anthropogenic sources and growth has to be considered.

Fig. 1Due to the high takes in the past of marine resources, targeting the large species or not, the mega-fauna has suffered and many of them are of such small quantities that many have become threatened with extinction. It is also harder to detect rates of decline from a smaller population using population growth models than with large populations (Figure 1). One also needs to sample the populations more often to be able to detect a decline. More sampling is equal to larger costs for researchers and at the end the government.

The data for Figure 1 is based on dugong populations in 91 survey blocks in the coastal waters of Queensland.

Management Considerations: It has been thoroughly studied that harvest, intentional or not, of long lived animals are not sustainable. Examples of harvest of long lived animals that has ended up as an catastrophy are the Orange Roughy, Atlantic Cod and many sea turtle species that all are threatened to extinction due to over harvesting. However, conservation efforts should target a sensible part of the life-cycle of the animal, e.g. in the turtles’ case; protecting turtle eggs from feral pigs and foxes and reduce take of mature female turtles from both the fisheries and indigenous people’s hunting.

A case study about Kemp’s Ridley Sea Turtles showed that a 100% egg harvest from a beach indicated a drastic decline in nesting females from more than 45.000 females per day before the World War II to in the 1980s as few as 500 females nested in the entire season. Conservation efforts were put in place to protect the eggs and hatchlings which resulted in an increase of survivorship from 0 to more than 60% and today we see an increase in new nests laid each year.

Trawling alone take unintentional more turtles than is sustainable for the populations. Add to this boat strikes, indigenous hunting both in and outside the boarders of Queensland. Removal of the highly inefficient fisheries in Queensland waters and indeed the rest of the world would result in a dramatic ecological gain globally for marine wildlife. Fisheries are subsidised to be able to continue trawling, which drives the harvest to even less sustainable levels.

Another great threat to turtles are shark- and gillnets. A majority of the above species will also be positively affected by removal of shark- and gillnets. The ecological gain from removal of such nets would also be great. Mortality of dugongs, dolphins and turtles would decline significantly. Social costs will play a role in this decision.

Recommendations: That the chairman:

  1. Introduce new legislation in conjunction GBRMPA and QEPA for a reduction and ultimately a stop of commercial fishing/trawling within the Great Barrier Reef Marine Park World Heritage Area.
  2. Develop a plan for alternative options e.g. marine ecotourism or equivalent and/or compensation in re-education of targeted persons to other options.
  3. With the assistance of GBRMPA’s and QEPA’s Aboriginal Liaison officers, work in conjunction with the local Indigenous Communities both in Australia and neighbouring countries to:
  1. Explain the reason for new legislation of reduction of the harvest of threatened species of marine wildlife, e.g. dugongs and turtles and the local community involvement in conservation of these species.
  2. Develop a plan for alternative options and/or compensation for this loss.

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