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Section 1: The Current Situation 24 This section outlines the current situation of New Zealand seaweeds by providing the best available information across the SOIs three broad outcomes: ♦ Health of the aquatic environment is protected ♦ Best value is able to be realized ♦ Credible fisheries management 25 Most seaweeds belong to one of three groups based on colour: the browns (phaeophytes), reds (rhodophytes), and the greens (chlorophytes). 26 The brown seaweeds are the largest and most conspicuous of the three seaweed groups and include kelps. Green and red seaweeds are typically smaller, and more frilly and delicate in structure. Conflict – one plural, one singular 27 Seaweeds generally comprise of three main parts: a holdfast, a stipe, and blades (or fronds) – refer to Figure 2 for illustration of each seaweed part and lifecycle. The stipe can be of considerable length to enable the blades to reach shallower water where light intensity is greater. Stipe is usually unable to support the weight of the blades out of the water. Green and red seaweeds are typically more filamentous or sheet-like in structure. 28 The life history comprises two main phases – the predominant (conspicuous) sporophyte phase (stage that produces asexual zoospores) and the inconspicuous gametophyte phase (stage that bears sexual gametes). There are species-specific variations in life history. Figure 2: A stylised diagram of the life history of a seaweed (illustration obtained from NIWA website at www.niwascience.co.nz) 9 HEALTH OF AQUATIC ENVIRONMENT PROTECTED 29 An understanding of the nature, diversity, stability, productivity, and the extent of New Zealand’s seaweed resources provides information to address fishing and non-fishing impacts on the aquatic environment. 30 Seaweeds are structurally important components of the aquatic environment. They play a vital role in the ecology of the aquatic ecosystems giving structure and complexity; providing substrate, food and shelter to many marine organisms; and contributing to the nutrient cycling of both beaches and the surrounding coastal waters. Seaweeds are critical for the recruitment, dispersal and protection of many commercially important fisheries such as rock lobster, paua and mussel spat. Managing the Effects of Fishing 31 The activity of fishing can impact the aquatic environment in a variety of ways. For example, bottom impacting fishing methods (eg, trawling and dredging) can alter the structure of the seafloor and impact associated plants and animals, and fishing nets or lines can inadvertently capture or injure marine mammals or seabirds. The Fisheries Act 1996 outlines several environmental principles that must be considered when making decisions relating to the use or sustainability of fisheries resources like seaweeds. These include: ♦ maintaining biological diversity (biodiversity) of the aquatic environment ♦ protecting habitats of particular significance for fisheries management. ♦ maintaining associated or dependant species above a level that ensures their longterm viability 32 In addition, in 2005 the Government launched its Strategy for Managing the Environmental Impacts of Fishing (SMEEF) The SMEEF proposed the development of a set of standards for defining acceptable limits of effects of fishing on the aquatic environment. The development of these performance standards is now underway. The following sections examine seaweed fisheries in relation to the environmental principles and linked performance standards. Fishing impacts on the seafloor (benthic impacts) are discussed as a separate topic as these impacts span both biodiversity and habitats of particular significance to fisheries management. Biological diversity Performance standard: Draft standard is to identify and maintain biodiversity in the aquatic environment. 33 Section 9 of the Fisheries Act 1996 outlines several environmental principles that all persons exercising or performing functions, duties, or powers under the Act, in relation to the utilisation of fisheries resources or ensuring sustainability, shall take into account. One of these environmental principles is to maintain biological diversity of the aquatic environment. 34 New Zealand’s marine biodiversity is to be protected by establishing a network of marine protected areas that is comprehensive and representative of New Zealand’s marine habitats and ecosystems. 10 35 The Government aims to achieve a “target” of 10% of New Zealand’s marine environment protected by 2010. MFish and the Department of Conservation are jointly responsible for developing and implementing marine protected area policy to achieve this target. There are a number of marine protected areas throughout New Zealand, including various closed areas and 31 marine reserves. 36 New Zealand has an extensive marine algal flora of about 1 000 species. Exposed reefs, channels and pools have the greatest diversity of seaweed species. Harbours, fiords, and sounds share some of this rich flora. Sheltered lagoons, mangroves, inlets and estuaries where the salinity is reduced by freshwater have a very different seaweed flora. In many of these habitats, a flowering plant commonly called seagrass (Zostera spp.) may be very extensive. Each of these natural habitats has a typical association of seaweed species that commonly vary in composition from north to south. 37 Seaweeds are critical for the recruitment and protection of many commercially important finfish and shellfish fisheries. Attached seaweeds are structurally important components of the marine environment and support high biodiversity by providing habitat, shelter and food, as well as affecting wave flow and energy. Many important finfish (eg, butterfish, moki) and shellfish (eg rock lobster, paua, kina) species generally associate with reef areas that predominate with large kelp forests. However, the interactions and associations between seaweeds and higher-order species are not well understood. 38 Free floating seaweeds play an important role in the recruitment and dispersal of other organisms. Beach-cast seaweeds provide habitat and food for a diverse ecology of marine and terrestrial organisms, as well as being key sources of nutrient cycling within the aquatic environment. It is estimated that up to 25% of the annual kelp production may become beach-cast, and, when not removed from the beach environment, this material can play a significant role in coastal ecosystems. 39 Each of the three seaweed states has different key implications on biodiversity. These key implications are set out in Figure 3. 40 The invasive Japanese seaweed Undaria pinnatifida is found in many parts of New Zealand (mainly restricted to parts of the southern North Island and throughout the South Island). This seaweed is known to displace many native seaweed species and has the potential to have negative implications for biodiversity of both seaweeds and non-seaweed species. There is presently a prohibition on the commercial harvest of Undaria. Biosecurity New Zealand, however, is to review this prohibition in 2007 and some commercial harvest may be allowed in the future. In some areas, regional authorities are taking limited measures to control the spread of this species. 11 Figure 3: Key characteristics of the three seaweed states and implications for biodiversity States Attached Free Floating Beach-cast Biological life-cycle Biodiversity ECOLOGICAL ROLE CANOPY FORMING CAN STILL BE GROWING AND REPRODUCING CRITICAL HABITAT IMPORTANT FOR RECRUITMENT OF MANY SPECIES IMPORTANT FOOD SOURCE AND SHELTER FOR INVERTEBRATES AND SHORE BIRDS DISPERSAL OF SPECIES STRUCTURAL IMPORTANCE MODIFYING WAVE FLOWS AND ENERGY SETTLEMENT SURFACE FOR MUSSEL SPAT REFUGE AREAS FOR JUVENILE AND LARVAL FISH NESTING MATERIALS FOR SEABIRDS/WADERS POTENTIAL BEACH BUILDING MATERIAL Habitats of particular significance to fisheries management Performance standard: Draft standard is to identify and protect habitats of particular significance for fisheries management. 41 Protecting habitats of particular significance to fisheries management is one of the environmental principles outlined in s 9 of the Fisheries Act 1996. 42 Seaweeds are found in all habitats of significance, including spawning and nursery areas, estuaries, and areas of particularly high biodiversity. Associated or dependent species Performance standard: Draft standard is to identify and maintain associated and dependent above a level that ensures their long-term viability 43 Maintaining associated or dependent species above a level that ensures their long-term viability is one of the environmental principles outlined in the Fisheries Act 1996. 44 Associated or dependent species means any non-harvested species taken or otherwise affected by the taking of any harvested species. This can include protected species such as marine mammals, seabirds, and reptiles. 12 Protected species 45 There are no direct associations between seaweed harvesting and fishing-related mortality of protected species. However, there are indirect associations between seaweed harvesting and several protected species, as presented below. Seabirds and reptiles 46 A wide range of invertebrates (eg, amphipods, isopods, copepods) are found living on beach-cast seaweeds. These invertebrates are an important food source for some protected birds and reptiles. For example, kiwi on Stewart Island are often found foraging for amphipods and isopods amongst beach-cast seaweeds. Although there are no quantitative New Zealand studies on the use of seaweeds by birds, overseas studies suggest that beach-cast seaweeds have a significant effect on density and abundance of some shorebird species. These studies indicate a positive correlation between beach-cast material abundance and seabird densities. 47 Many birds use beach-cast seaweeds for nesting either directly within the wrack material or to supplement other nesting material. The removal of beach-cast seaweeds from areas adjacent to seabird breeding colonies could affect the breeding success of some seabird species. 48 Several native skink and gecko species also feed on the invertebrate communities that inhabit beach-cast seaweeds. A reduction or removal of beach-cast seaweeds may have negative implications on these species. Benthic impacts Draft standard will define the permissible level of impact of fishing methods on each habitat identified. 49 Benthic impacts are impacts on the animals and plants living on, or attached to, the bottom of the sea, lake or river from high water mark down to the deepest levels (ie, the benthos). 50 There are currently no New Zealand studies to assess the direct impacts of seaweed harvesting on the benthic environment. Nearly all commercial and non-commercial seaweed harvesting is currently undertaken by handgathering methods only (ie, picking, raking, scooping). Some limited cutting of bladder kelp (Macrocystis) occurs on the Chatham Islands. Some trials have also been undertaken in Akaroa Harbour to investigate the effects of floating mechanical harvesters on bladder kelp. 51 Areas with high kelp biomass (commonly referred to as ‘forests’ or ‘stands’) form important structural components in inshore and coastal areas. These kelps typically modify wave flow and energy; hence their removal can have large-scale implications to the physical structure of inshore areas, largely through erosion and reduced beach-building. A large-scale harvest of kelps could increase erosion in localised areas and impact on beach building processes. 52 Research undertaken in Australia suggests the following potential adverse effects may arise from the large-scale removal of beach-cast seaweeds from an area. a) Loss of nutrients from the inshore and coastal systems through the nutrient recycle process. 13 b) Removal of an important food source and shelter for invertebrate and seabirds. c) Loss of nesting material for seabirds. d) Removal of potential beach-building material, as beach-cast seaweeds are effective at trapping wind-blown sand and reducing erosion. 53 Conversely, removal of infestations of aquatic seaweeds in ponds and lakes that have high nutrient conditions could provide some positive outcomes for biodiversity and the benthic communities in such habitats. Other resource users 54 Regional Councils manage the effects of land-based activities on the marine environment such as changing land-use (ie, forestry, town development, etc.). Increases in nutrient run-off into coastal waters from agricultural development may lead to greater proliferation of seaweed beds. Increased sediment load within localised waters may lead to seaweed bed die-off or reduced growth, productivity, etc. through increased water turbidity (eg, reduced light penetration) and smothering. 55 Several local authorities and regional councils regularly remove decomposing/rotting beach-cast seaweeds from popular beaches throughout New Zealand for sanitation and aesthetic purposes. In addition, power companies regularly clean up freshwater algal build-up round turbine intake tubes. 56 Seaweeds are increasingly being on-grown on marine farms in many parts of New Zealand. The effects of seaweed farming on the aquatic habitat are unknown. Seaweed farming may be beneficial by increasing productivity (ie, greater concentrations of chlorophyll within the water) and increasing number of reproductive spores. However, decaying seaweeds under farms may have negative effects within localised areas. Specifying Limits on Fishing Activity Harvest Strategies Draft harvest strategy standards (s 13 or s 14) 57 As seaweeds are managed outside the Quota Management System (QMS), there is no prescribed target level for each seaweed stock. 58 MFish has not imposed a total catch limit for any individual seaweed stock due to the current low level of seaweed catches. 59 The principle harvest strategy for seaweeds is to provide for utilisation while ensuring sustainability. 14 Stock assessment information Biological characteristics 60 Table 1 below provides an overview of the lifecycle, growth, preferred habitat and distribution of the main seaweed species. More detailed biological and stock assessment information is provided in Appendix 1. 15 Table 1: Species Macrocystis pyrifera Key biological characteristics of the main seaweed species Seaweed group Brown Life cycle 2 phases: Conspicuous sporophyte kelp phase, microscopic gametophtye phase Growth Lessonia spp. Brown Durvillaea antarctica Brown Porphyra species Red 2 phases: Conspicuous sporophyte kelp phase, microscopic gametophtye phase Direct life history with separate male and female seaweeds producing eggs and sperm. Reproduction from late autumn to early spring Large conspicuous gametophyte phase and a small sporophyte phase Winter annual Perennial Grow up to 20 m high Worlds fastest growing plant, up to 0.5 m/day Temperature and light limited Maximum biomass occurs in winter Perennial Grow up to 1 m high Habitat type Found on rock in calmer bays, harbours and offshore reefs Distribution Southern North Island at and south of Castle Point and Kapiti Island South Island and Stewart Island, Chathams and others Found on rock from low water spring to sub-tidal on very exposed coasts Throughout New Zealand Plants massive grow up to 10 m but usually 3-5 m high Seaweed may be 10 years old Found on rock forming a broad zone at low water in very exposed situations, but also extending into calmer bays Throughout New Zealand but is most common south of Cook Strait. Usually grow ca. 15-25 cm Some species are epiphytic Growth and longevity very species specific Species specific ranges from upper intertidal rocks in moderately sheltered to open sites to epiphytic on Durvillaea species Throughout New Zealand Species Gracilaria chilensis Ecklonia radiata Seaweed group Red Life cycle An alteration of sporophyte and dioecious gametophyte generations Usually grows ca. 15-25 cm Forms persistent mats, often detached from substrate • Brown 2 phases: Conspicuous sporophyte kelp phase, microscopic gametophtye phase Grow up to 1 m or more high Growth of recruits inhibited by high light intensity Is winter fertile Grow from 10 – 50 cm Grows up to 30 cm high Pterocladia spp. Red Ulva spp. Green An alteration of sporophyte and dioecious gametophyte generations Sporophyte releases spores that grow in to male or female gametophytes that are morphologically indistinguishable from the sporophyte. The gametophyte releases gametes that fuse to form the zygote that settles and grows into a sporophyte Growth 17 Habitat Found in sheltered sites frequently in harbours and estuaries and often in areas with muddy sands. Grows attached to shell as well as on cobbles and rocks, in the low intertidal zone through to the upper sub-tidal (to ca. 1-2 m) Found on rock at and below low water spring on moderately sheltered and exposed coasts Found on rock at and below low water spring on exposed coasts Found on rock and solid substrate. Intertidal in moderately sheltered areas. Sometimes free-living Distribution Throughout New Zealand Throughout New Zealand Throughout New Zealand Throughout New Zealand Indices of stock abundance and biological information 61 Varying amounts of biological information are available for a number of New Zealand macro-algae species. However, there is limited, to no, information available in regards to stock abundance, relative or absolute biomass estimates, catch per unit effort (CPUE) or catch trends for any seaweed species or stock. Research 62 Completed research projects on seaweeds include: Year 2001 Research project Assessment of Pterocladia lucida at Waihau Bay, New Zealand. New Zealand Fishery Gerring, P.K., Andrew, N.L. and A. Dunn (2001). Assessment Report 2001/72. 23 pp. 2005 Beach-cast seaweed: a review Zemke-White W L, Speed S R, McClary D J, New Zealand Fisheries Assessment Report 2005/44 August 2005 Total allowable catch 63 There are no total allowable catches (TACs) for any seaweed stock. Annual or seasonal commercial catch limits do not apply to any seaweed stock, and no explicit allowances have been made for non-commercial fishers.