Marine Fish and InvertebratesDiversity, threats, and trends

Alison MacDiarmid

NIWA, Wellington

NZ’s marine realm

• Includes the Territorial Sea, EEZ and ECS

• Totals 5.7 M km2

• An area 21 larger than the NZ land mass

• Comprises almost 1.7% of the worlds oceans

• Extends from the sea surface to >10 km depth; a total volume of ~11.4 M km3

New Zealand has a varied and complex

seascape

► New Zealand- a small part of a large submerged continent – Zelandia

► Huge variety of seascapes; a consequence of…

o Location on active boundary of two great tectonic plates

o Extension over 30o of latitude from subtropics to sub-Antarctic

o Complex coastline

o Bathed in warm and cool surface currents and very strong deepwater currents

NZ seafloor complexity vs Australia

Seafloor and oceanographic complexity has produced many distinct habitats

Complex seascape and isolation means high

biodiversity and endemism• 17,135 known species including

4,315 undescribed species.

• Estimates of the number of species still to be discovered ranges from another 17,000 – 34,000

• Species diversity is roughly equivalent to that recorded in the European Register of Marine Species which covers an area approximately 5.5 times larger.

• Levels of endemism at 44% overall is high from a global perspective and in some groups is very high; sponges (95%), molluscs (84%), ascidians (75%), bryozoans (>60%)

Implications of high levels of marine endemism

► The large number of undescribed and unknown marine species in NZ’s realm makes the task of determining impacts more difficult. Species may be affected by a range of pressures before their presence is known.

► The high levels of endemism in many taxa means that NZ cannot be reliant upon the good stewardship of marine biodiversity in neighbouring countries or areas to maintain our environments.

► This need for self-reliance challenges New Zealand policy and strategy development to maintain the integrity and long-term sustainability of the environments and habitats in which New Zealand’s marine species occur.

White sharksMost NZ white sharks make annual migrations to tropical waters in winter, travelling as far as 3,300 km away.

Sharks have migrated to the Great Barrier Reef in Australia, the Coral Sea, New Caledonia, Vanuatu, Norfolk Island, Fiji and Tonga.

Highly migratory species

NZ’s management and policy actions need to include close and continued collaboration with countries and agencies responsible for management and conservation of these trans-jurisdiction species

A short history of exploitation

► Humans arrived in NZ 800 years ago with established fishing technologies

► The impact of small human populations, first Māori then European, on vulnerable species was rapid and dramatic

► Populations of some marine mammals, seabirds, fish, and invertebrates are still depressed.

► Unlike the terrestrial ecosystem few species went extinct (1 petrel, 1 penguin, 1 shag sub-species and possibly the northern sea lion)

► Modern controls on catches are allowing populations of some species to rebuild (e.g. snapper) and some extirpated species extending back into areas not considered in modern times to be suitable habitat – e.g. NZ fur seals

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Landed value, NZ wetfish, $/ton

Hauraki Gulf mussel landings (t)

Legacies: Collapse of the green mussel dredge fishery

Ecological consequences- Loss of reef like structure- Loss of filtration capacity

Restoration possible?

(From Paul 2012)

Depressed biomass of fished species

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Greater Hauraki Gulf

Fishing is just one of many threats to New Zealand’s marine environment

Top 20 threats over all New Zealand marine habitats (maximum score = 4) GCC = Global Climate Change

GCC- Ocean acidification 2.6 Algal blooms – both toxic and massive 0.9

GCC - Increasing sea temperature 1.6 Increased turbidity 0.9

Bottom trawling 1.5 Recreational line fishing 0.8

Sedimentation 1.5 Coastal reclamation 0.8

GCC - Changed currents 1.2 GCC – Increased stratification 0.8

GCC – Increased storminess 1.2 Sewage 0.8

Scallop/oyster dredging 1.0 Nitrogen and Phosphorus 0.8

Dumping of dredge spoils 0.9 Petroleum 0.8

GCC – Sea level rise 0.9 Potting or trapping 0.7

Invasive species – space occupiers 0.9 Long-lining 0.7

Expert risk assessment of 65 threats to each of 57 NZ marine habitats:

Anthropogenic Threats► These results may be useful in identifying which threats require the

highest research priority and which habitats should be the first focus for management action.

► There is likely little or nothing NZ marine managers can do to directly control ocean acidification or any of the threats stemming from global climate change.

► However, we can and should document their impacts on marine habitats and deliver these results not only to the science community but also to those negotiating the global control of greenhouse gases.

► There is more hope for better management and control of catchment and marine based threats to marine habitats as these are under New Zealand’s jurisdiction.

► Success in this area may enable marine ecosystems to better withstand the global threats of ocean acidification and climate change that are highly likely to intensify throughout this century.

Conclusions

► NZ’s marine environment is vast and largely unexplored

► Compared to the terrestrial situation availability of environmental information is decades behind

► High levels of endemism and highly migratory species both pose particular management issues

► Human impacts started late compared to most other places

► A wide range of human activities affect NZ marine ecosystems

► Threats deriving from global and catchment based activities comprise 2/3 of the top 20 threats

► Marine managers can directly address only about 1/3 of key threats

► Addressing others will take global and regional efforts