Posts

Posted on

Ten reasons why MPs should support Gulf protection bill

Snapper Goat Island

Recreational fishing lobbyists LegaSea are making a last ditch effort to stop the Hauraki Gulf / Tīkapa Moana Marine Protection Bill. Here are ten reasons why Scott Simpson and other MP’s should support the bill as it stands:

  1. Broad Public Support for Protection: There is overwhelming public support for marine protection. The bill will increase protection from 0.3% to 6%. 77% of the public want much more (30%) of the Gulf protected.

  2. eNGO Support for Increased Protection: Environmental groups have consistently asked for more protection than the bill currently provides, indicating that the bill is already a compromise aimed at balancing diverse interests​.

  3. Protection to Address Depletion and Habitat Damage: The bill addresses overfishing, habitat destruction, and declines in marine biodiversity in small areas. Lage scale bottom-impact fishing​ is being delt with through a different process.

  4. Scientific Evidence Supports High Protection Areas (HPAs): While recreational fishers claim there is no evidence to support HPAs, scientific studies worldwide demonstrate that protected areas are fantastic for restoring fish populations and biodiversity​.

  5. Minimal Economic Impact on Recreational Fishing: Recreational fishers will still have access to 87.4% of the Gulf for fishing. The HPAs cover a small portion, reducing the impact on fishing activities while promoting long-term marine ecosystem health​.

  6. Displacement Concerns Are Overstated: The limited fishing restrictions introduced by the bill are offset by gains in fish abundance in nearby areas, as larger, reproductively mature fish spill over into fished zones, ultimately benefiting fish stocks outside HPAs.

  7. Limited and Controlled Commercial Fishing: The bill may include ring-net fishing in two HPAs compromising their objectives. However, 10 high protection areas and the two marine reserve extensions will be unaffected by the amendment.

  8. Ecosystem Benefits for Seabirds and Marine Species: High Protection Areas will help protect seabird foraging grounds and marine ecosystems, which directly impacts terrestrial food webs and biodiversity on islands in the Gulf.

  9. Strong Legislative Foundations: The bill aligns with New Zealand’s marine protection obligations under international agreements, reflecting a responsible approach to safeguarding marine biodiversity while considering local cultural and socio-economic factors​.

  10. A Balanced Approach to Sustainable Use: This bill offers a compromise between no-fishing reserves and managed-use areas, establishing a multi-use marine park with regions for both recreational fishing and high protection. This approach meets both conservation and fishing community interests without entirely prohibiting either​.
Posted on

First look at the Bream Bay sand mining area

When I saw the proposed new Fast-track sand mine in Bream Bay placed on a map by Marc Daalder I thought I would have a look at the site.

I launched my kayak from Uretiti Beach and paddled 6.5 km to the site. On the way I paused six times to drop a weighted GoPro on timelapse from a dive line to photograph the seafloor. I then paddled South West of the mining site and took 12 more photos in a 1km North East transect.

I was not expecting to see much benthic biodiversity as the area is frequently trawled. However I was very pleased to find extensive non-calcareous tubeworm fields (Spionidae – I think) in half the photos, mostly at the north-eastern end of the transect. The filter-feeding tubeworms are a good sign the seafloor is stable and able to support even more complex biogenic habitats if trawling pressure was removed. (Sand mining directly and indirectly impacts biogenic habits, these complex 3D structures made by life on the seafloor are easily buried by unstable substrate.) The tubeworm fields are also associated with tipa / scallops. I was only clearly able to identify one live tipa in the 12 photos but tipa shells were a common feature of the area.

It was a quiet afternoon on the surface with no workups seen, however single tākapu / gannets were working the area, I counted five kororā / little penguin on the way to the site and a tight ball of forage fish.

tipa shells
large ostrich foot snail
live tipa
tight ball of forage fish
tubeworm field
tubeworm field

Posted on

Brief for restoring extremely degraded seafloor ecosystems

Degraded seafloor - sediment - mudification

I don’t know how to solve this problem, so I am writing it up as a public brief for people smarter than me.

Brief for restoring extremely degraded seafloor ecosystems

Soft sediment marine ecosystems support diverse and productive biogenic habitats like shellfish beds, sponge gardens, tubeworm fields, and bryozoan mounds. Direct impacts such as mobile bottom contact fishing, and indirect impacts such as sediment pollution, reduce the function of these habitats. Stopping or reducing the impacting activities can help the habitats recover naturally over many decades. Active restoration (like mussel and oyster seeding) can be done in areas where the habitat is not recovering naturally; however, some environments can be too degraded for these methods.

Problem

In my opinion, at least tens of square kilometres of the Hauraki Gulf Marine Park are too degraded to restore with known techniques. In these extremely degraded areas, the seafloor is very soft, deep mud. It’s not lifeless; there are burrows and infauna present. But the areas would be more diverse and productive if the seafloor was less soft with less sediment in suspension. Even when pollution input has been reduced in these extremely degraded areas, legacy sediment is constantly resuspended – choking filter-feeding animals and smothering photosynthesising plants. It is difficult to visually convey the condition of these ecosystems, as visibility is usually less than 30 cm on a good day.

Solutions

To increase biodiversity in these areas, the benthic enhancement method must be low-cost at scale. This means traditional erect concrete and steel structures are not likely to be the solution. In my opinion, resurfacing the seafloor with demolition rubble or quarried aggregate is too extreme because it kills all the infauna. Anything heavy deployed will immediately sink into the mud, anything lighter than the mud will quickly be covered by sediment. A smarter solution might contain one of these elements:

  • Local pits or trenches to collect the most mobile sediment.
  • Dispersed erect artificial shellfish (think horse mussels) to slow benthic currents and allow sediment to fall out of the water column in fields or fences.
  • Regular deployments of waterlogged woody debris.
  • Biological concrete structures that grow using elements from the local environment.
  • Hardened local seafloor sediments (think mudbrick or mudcrete).
  • Growing dense algae at the surface which will 1) slow currents and surge to reduce resuspension 2) drop fragments for sequestration, feeding invertebrates, collecting sediment and seafloor hardening.

Caution

While these solutions will restore some ecosystem function they will not restore the original ecosystems. Hard surfaces will likely be first colonised by invasive species and the new habitat will offer more ecosystem services but be novel / new. We must first halt the destructive activities that degraded the seafloor ecosystems.

Posted on

Oil spill trajectory modelling from the wreck of the RMS Niagara

RMS Niagara oil spill trajectory during summer conditions

I asked Maritime NZ for the oil spill trajectory modelling from the wreck of the RMS Niagara. I have uploaded it here for anyone interested.

Oil spill trajectory modelling from the wreck of the RMS Niagara

My layman’s notes below:

MNZ have kindly tried to explain it to me, but I don’t really understand why the 2016 modelling was only done with about 97 tonnes of oil (100 m³) when the Rena leaked 350 tonnes. The RMS Niagara could store more than 4,000 tonnes of oil and experts have estimated that there could be 1,400 tonnes remaining. This means the estimated volume of oil on individual beaches and the length of shoreline impacted could be dramatically worse.

The probability of oil contact with the shoreline increases by 10% if it happens in summer (This is tara iti / New Zealand fairy tern breeding season, we are down to nine breeding female left, note the Rena spill killed 2,000 birds). The impacts move a bit further south in winter.

It’s interesting to see the areas impacted. The spill expands outward from the wreck largely as you would expect, but there are interesting details. For example, it will be twice as bad at Goat Island than further up the coast at Mangawhai. If it’s going to be visible at the Mokohinau Islands in just a few hours, I think it might be a good idea to install a webcam there.

Harbours and bays are less impacted, but I wonder if this is an artefact of the modelling software. It definitely shows that even a 97-tonne spill will span a massive length of our coastline. For example, Waikato Regional Council also needs to be prepared.

I’d like a better understanding of the risk and the mentioned contingency plan. It would be helpful to run scenarios with different response times, gear, and methods; this may have already been done.

Posted on

Turtles of Aotearoa

Turtles of Aotearoa 7 species of sea turtle in the world 5 recorded in New Zealand 2 more frequently seen here Nearest nest sites in Australia and New Caledonia Navigate using earths magnetic field Forage near the coast eating algae and sea slugs Threatened with extinction, dying here from marine plastic boat strike and fishing The regional subpopulation is expected to go extinct in 40-80 years Nest in Papua New Guinea, and Solomon Islands Forage offshore on jellies in the water Frequently caught by tuna fishers, with no efforts to reduce bycatch in leatherback hotspots Up to 1.5 m long Up to 2.7 m long Green sea turtles Leatherback sea turtles Loggerhead Green Leatherback Olive Ridley Hawksbill

After finding a green sea turtle in Devonport and reading about leatherback sea turtle bycatch I decided to do some research on what was going on with turtles in New Zealand. I made a graphic summary.

Turtles of Aotearoa 7 species of sea turtle in the world 5 recorded in New Zealand 2 more frequently seen here Nearest nest sites in Australia and New Caledonia Navigate using earths magnetic field Forage near the coast eating algae and sea slugs Threatened with extinction, dying here from marine plastic boat strike and fishing The regional subpopulation is expected to go extinct in 40-80 years Nest in Papua New Guinea, and Solomon Islands Forage offshore on jellies in the water Frequently caught by tuna fishers, with no efforts to reduce bycatch in leatherback hotspots Up to 1.5 m long Up to 2.7 m long Green sea turtles Leatherback sea turtles Loggerhead Green Leatherback Olive Ridley Hawksbill
Turtles of Aotearoa

Big thanks to Clinton Duffy for the review.

Posted on

Artificial Reef or Fish Aggregation Device?

Artificial reefs have significant potential to boost fish populations, even surpassing pre-fished levels or what is possible in marine reserves. However they have a checkered history overseas, with many reefs:

  • Failing to restore native biodiversity to levels of those of conserved natural reefs (Bracho-Villavicencio et al. 2023).
  • Creating hard surfaces which are favoured by invasive species (these species often travel to new areas on hard structures) (Gauff  et al. 2023).
  • Created as a convenient way to dispose of something which pollutes the marine environment (E.g. UnderwaterTimes.com 2006). They can also attract polluting activities (Zhang et al. 2019).

When considering building an artificial reef, it is crucial to determine whether it will provide additional habitat to support reef communities or merely function as a Fish Aggregation Device (FAD). Like artificial reefs, FADs are man-made structures which are attract fish to a specific area by providing habitat and shelter for marine life. The problem with FADs is that they decrease local fish populations by concentrating them in one area where they are easily targeted by fishers (Cabral et al. 2014) as illustrated below.

To define the size of the habitat required to avoid FAD functionality, you could base it on the home range of each fish species you want to increase. For example:

The most studied fish in the Hauraki Gulf is the tāmure / snapper, which show high site fidelity to reef habitats. Tāmure in deep soft sediment habitats are quite mobile, with a median distance of 19 km, and some movements up to 400 km. In contrast tāmure in shallow rocky reef habitats have restricted movements, with a median distance of 0.7 km (Parsons et al. 2011). You can see this in small marine reserves with shallow rock reefs, such as the 5 km² Cape Rodney – Okakari Point Marine Reserve (Goat Island), which effectively increase the size and abundance of this species. Additionally, tāmure around mussel farms have been found to be healthier than those in surrounding soft sediment habitats (Underwood 2023). The studied mussel farms were near rocky reefs and covered about eight hectares (200 x 400m).

This means fished artificial reefs should be deployed at hectare scales to avoid acting as population sinks. For tāmure, an area about the size of eight rugby fields is a considerable undertaking, but to avoid your reef functioning as a FAD for fishing, it is essential to spread your structure over a large area. If this sounds more like ‘habitat enhancement’ than an artificial reef, then perhaps that is a better way to frame your design. Of course, this consideration is unnecessary if your artificial reef is not fished.

REFERNCES

Bracho-Villavicencio et al., 2023 https://doi.org/10.3390/environments10070121 A Review of the State of the Art and a Meta-Analysis of Its Effectiveness for the Restoration of Marine Ecosystems. Environments.

Cabral et al., 2014 https://academic.oup.com/icesjms/article/71/7/1750/664488 Modelling the impacts of fish aggregating devices (FADs) and fish enhancing devices (FEDs) and their implications for managing small-scale fishery

Gauff  et al., 2023 https://doi.org/10.1016/j.jembe.2023.151882
Unexpected biotic homogenization masks the effect of a pollution gradient on local variability of community structure in a marine urban environment.

Parsons et al., 2003 https://www.researchgate.net/publication/225304000_Snapper_Pagrus_auratus_Sparidae_home_range_dynamics_Acoustic_tagging_studies_in_a_marine_reserve Snapper Pagrus auratus (Sparidae) home range dynamics: Acoustic tagging studies in a marine reserve

UnderwaterTimes.com 2006
https://web.archive.org/web/20170912095117/https://www.underwatertimes.com/news.php?article_id=36210951740 Two Million Tire Artificial Reef to be Removed Off Florida Coast; Smothering Corals

Underwood et al., 2023 https://www.aquaculturescience.org/content/dam/tnc/nature/en/documents/aquaculture/AquacultureHabitatComparativeReport.pdf  Habitat value of green-lipped mussel farms for fish in northern Aotearoa New Zealand

Zhang et al., 2019 https://doi.org/10.1016/j.scitotenv.2019.134768
Microplastic pollution in water, sediment, and fish from artificial reefs around the Ma’an Archipelago, Shengsi, China.