NEW ZEALAND COCKLES. Austrovenus stutchburyi. Sometimes known as Littleneck Clam, Cockle, Venus Shell, Tuangi SUMMARY

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1 NEW ZEALAND COCKLES Austrovenus stutchburyi Sometimes known as Littleneck Clam, Cockle, Venus Shell, Tuangi SUMMARY New Zealand Cockles are a fast growing species of shellfish found in harbors and estuaries throughout the country. Most populations have a healthy abundance. New Zealand Cockles are mostly collected by hand picking, which causes little habitat damage and results in low levels of bycatch. In some areas, their habitat has been negatively affected by increased sedimentation, urban development and industrial contamination. While they can recolonize an area after a disturbance, the success of recolonization varies greatly between locations. Criterion Points Final Score Color Life History Abundance Habitat Quality and Fishing Gear Impacts Management 1.50 Bycatch 3.50 Final Score 2.65 Color

2 LIFE HISTORY Core Points (only one selection allowed) If a value for intrinsic rate of increase ( r ) is known, assign the score below based on this value. If no r-value is available, assign the score below for the correct age at 50% maturity for females if specified, or for the correct value of growth rate ('k'). If no estimates of r, age at 50% maturity, or k are available, assign the score below based on maximum age Intrinsic rate of increase <0.05; OR age at 50% maturity >10 years; OR growth rate <0.15; OR maximum age >30 years Intrinsic rate of increase = ; OR age at 50% maturity = 5-10 years; OR a growth rate = ; OR maximum age = years Intrinsic rate of increase >0.16; OR age at 50% maturity = 1-5 years; OR growth rate >0.30; OR maximum age <11 years. New Zealand Cockles reach sexual maturity around 18 mm in shell length (MFish 2007a) and may live up to 20 years (Owen 1992). New Zealand Cockles grow quickly. For example, growth rates from Pakawau Beach (South Island) range from 0.36 to 0.41 (Osborne 1992; 1999) while estimates from Whangarei Harbor (North Island) range from 0.26 to 0.31 (Cryer et al. 2004; Williams et al. 2006). It has been estimated to take 3 or 5 years for New Zealand Cockles to reach 30 mm, which is a typical market size (Martin 1984). There is some evidence that New Zealand Cockles found in areas with lower densities grow faster than those found in areas of high densities (MFish 2007a) and growth rates in estuaries can vary based on different conditions (Marsden and Adkins 2010). Growth can also be impacted by tidal height and location on the shore. For example, Dobbinson et al. (1989) and Osborne (2010) found that New Zealand Cockles found on higher shore areas grew slower than those found lower on the shore. Growth rates can also be slower in areas with reduced salinity, areas with fine sediment and areas with a large amount of contaminants (Marsden and Adkins 2010). Points of Adjustment (multiple selections allowed) Species has special behaviors that make it especially vulnerable to fishing pressure (e.g., spawning aggregations; site fidelity; segregation by sex; migratory bottlenecks; unusual attraction to gear; etc.). New Zealand Cockles are fairly mobile while they are small but once they reach 25 mm in size they remain mostly in one place (MFish 2007a), making them easy for fishermen to target.

3 -0.25 Species has a strategy for sexual development that makes it especially vulnerable to fishing pressure (e.g., age at 50% maturity >20 years; sequential hermaphrodites; extremely low fecundity) Species has a small or restricted range (e.g., endemism; numerous evolutionarily significant units; restricted to one coastline; e.g., American lobster; striped bass; endemic reef fishes). New Zealand Cockles are found in estuaries and harbors throughout the North and South Islands, Stewart Island and the Chatham Islands (Morton and Miller 1968). New Zealand has the 10th largest coastline, of approximately 15,000 km, so cockles have a medium distribution range thus no points were subtracted Species exhibits high natural population variability driven by broad-scale environmental change (e.g. El Nino; decadal oscillations) Species does not have special behaviors that increase ease or population consequences of capture OR has special behaviors that make it less vulnerable to fishing pressure (e.g., species is widely dispersed during spawning) Species has a strategy for sexual development that makes it especially resilient to fishing pressure (e.g., age at 50% maturity <1 year; extremely high fecundity). New Zealand Cockles begin spawning in the spring and continue through the summer months (MFish 2007a). They are highly fecund, releasing a large number of eggs at a time into the water column Species is distributed over a very wide range (e.g., throughout an entire hemisphere or ocean basin; e.g., swordfish; tuna; Patagonian toothfish) Species does not exhibit high natural population variability driven by broad-scale environmental change (e.g., El Nino; decadal oscillations) Points for Life History

4 ABUNDANCE Core Points (only one selection allowed) Compared to natural or un-fished level, the species population is: 1.00 Low: Abundance or biomass is <75% of BMSY or similar proxy (e.g., spawning potential ratio) Medium: Abundance or biomass is % of BMSY or similar proxy; OR population is approaching or recovering from an overfished condition; OR adequate information on abundance or biomass is not available. New Zealand Cockle populations are at or above target levels and it is unlikely that they are depleted, collapsed or undergoing overfishing (MFish 2011a). In Waitati Inlet (South Island) for example, the Current Annual Yield (CAY) is above the current catch levels and reported landings (MFish 2009). However, there is some uncertainty surrounding the population sizes for some areas. In Tapu Bay, Ferry Point and Pakawau (South Island), for example, biomass levels that will support the maximum sustainable yield (MSY) are not known and therefore it is unknown if current catches or catch limits will support MSY (Osborne 2010). In Whangarei Harbor (North Island), the biomass was at 41% of its virgin biomass in 2005 (Williams et al. 2006). However, based on length frequency data from 2005, it appears that if fishing were kept at recent levels, the population could be sustained in the short but not long term (Williams et al. 2006). Although abundance of Cockles appears healthy throughout most of their range in New Zealand, we have assigned a middle score to account for the uncertainty and low biomass levels in some areas High: Abundance or biomass is >125% of BMSY or similar proxy. Points of Adjustment (multiple selections allowed) The population is declining over a generational time scale (as indicated by biomass estimates or standardized CPUE) Age, size or sex distribution is skewed relative to the natural condition (e.g., truncated size/age structure or anomalous sex distribution). There have been some changes in the size distribution of New Zealand Cockles over time but not in all areas. For example, the length frequency from Snake Bank, Whangarei Harbor, has remained similar in recent years, with Cockles slightly under 30 mm dominating the surveys (Williams et al. 2006). Although it appears the biomass of New

5 Zealand Cockles <30 mm has increased since 2004 (year of last survey) (Williams et al. 2006). In Ferry Point, the mean size has declined since 1996 but the biomass of small New Zealand Cockles in Tapu Bay, has increased since 2004 (Osborne 2010). In Waitati Inlet, the 2007 abundance of adults was more than that seen in 2004 but less than in 1998 and the abundance of large adults (<30 mm) was lower in 2007 than in 2004 (MFish 2009). In Pauatahanui Inlet (North Island), there has been an increase in large New Zealand Cockles at high and lower-mid tide since 2004, while at upper-mid tide the trend has been variable (Michael 2008). There is additional information that suggests some natural populations from both the North and South Island are skewed relative to optimum conditions (Anonymous 2011) so we have subtracted points Species is listed as "overfished" OR species is listed as "depleted", "endangered", or "threatened" by recognized national or international bodies Current levels of abundance are likely to jeopardize the availability of food for other species or cause substantial change in the structure of the associated food web The population is increasing over a generational time scale (as indicated by biomass estimates or standardized CPUE). Abundance levels of New Zealand Cockles over time vary by location. For example, abundances of New Zealand Cockles (>35 mm) in Snake Bank, Whangarei Harbor, in 2005 were the second highest on record and near double the 2001 estimate (Williams et al. 2006). Abundances of smaller animals (<30 mm) were higher than those found in the 1980 s and one third more than the average since 1990 (Williams et al. 2006). In Pakawau, the biomass of New Zealand Cockles is high compared to those from 1991 (Osborne 2010). However, the biomass from Tapu Bay has declined since 1991 and since 1996 in Ferry Point, although changes since 2004 (fishing has not really occurred in these areas since then) have been minimal (Osborne 2010). Abundances in Waitati Inlet were higher in 2007 but still below the 1992 levels (MFish 2009) and the density of New Zealand Cockles at Pauatahanui Inlet in 2007 was half the density in 1976, although the trend has been fairly stable since 1992 (Michael 2008). In the Northeast region, New Zealand Cockle populations at 16 beaches were assessed from 1992 to 2005 and it was found that the population trend was decreasing in two locations (Waiotahi and Umupuia), was increasing in one (Te Haumi) and could either not be assessed or no change was noted in the remaining locations (MFish 2007a). We have not added points due to the variability in trends between locations Age, size or sex distribution is functionally normal Species is close to virgin biomass.

6 +0.25 Current levels of abundance provide adequate food for other predators or are not known to affect the structure of the associated food web. New Zealand Cockles are considered an important food source for many fish, crabs and seabirds in both estuaries and harbors (Wilson et al. 1988; MFish 2007a). They are suspension feeders that feed on organic matter they filter out of the water column, and this food source can come from red algae, sea lettuce or microalgae (Leduc et al. 2006). Crabs, whelks and seabirds commonly prey on New Zealand Cockles (MFish 2008). Predation by birds is increased when New Zealand Cockles are parasitized by a common trematode, which infects their feet and impairs their ability to burrow (Thomas and Poulin 1998; Mouritsen 2002). In addition, when New Zealand Cockles become covered with macroalgae or ghost shrimp and lungworms disturb the soil, they must travel further to burrow, during which time fish crop their feet, making it impossible for the New Zealand Cockle to burrow, thereby increasing predation rates by shore birds and whelk (Mouritsen 2004). It is thought that this foot cropping is likely to affect New Zealand Cockles population dynamics (Mouristen and Poulin 2003). Research from Golden and Tasman bays, on muddy substrate that had high New Zealand Cockle densities, showed that after harvesting, foraging by shorebirds, including the protected variable oystercatcher, declined (Schnechel 2001). New Zealand Cockles make up the majority of prey of variable oystercatchers (Baker 1969) and therefore changes in the abundance of New Zealand Cockles is likely to affect variable oystercatcher s food supply. Since levels of New Zealand Cockles are currently healthy, they should provide adequate food supply to their predators Points for Abundance HABITAT QUALITY AND FISHING GEAR IMPACTS Core Points (only one selection allowed) Select the option that most accurately describes the effect of the fishing method upon the habitat that it affects 1.00 The fishing method causes great damage to physical and biogenic habitats (e.g., cyanide; blasting; bottom trawling; dredging) The fishing method does moderate damage to physical and biogenic habitats (e.g., bottom gillnets; traps and pots; bottom longlines).

7 3.00 The fishing method does little damage to physical or biogenic habitats (e.g., hand picking; hand raking; hook and line; pelagic long lines; mid-water trawl or gillnet; purse seines). In Whangarei Harbour, fishermen are restricted to hand gathering of Cockles but do use hand sorters, which separate out different sized animals along with silt (Williams et al. 2006). New Zealand Cockles are also harvested through commercial hand picking at Papanui and Waitati Inlets, Otago (MFish 2008) and in the Northeast region, there is a small commercial fishery in Ohiwa Harbor (MFish 2007a). The hand harvesting technique relies on a steel basket that is worked into the sand, pulled through the substrate, lifted and the contents are then shaken onto a sorting tray (Irwin et al. 2003). Fishermen also use mechanical harvesters at Pakawau, Ferry Point and Tapu Bay (Osborne 2010). Mechanical harvesting consists of a low pressure tyred harvester that removes the top 5-10 cm of substrate, which contains the New Zealand Cockles, and then passes them over a sorting grate (Schmechel 2001). Mechanical harvesting does have some negative impacts on the substrate including mixing of anoxic layers of mud and upper layers and chemical changes in the sediments that can inhibit recolonization (Schmechel 2001). There is also concern that mechanical harvesting could negatively impact eel grass beds and non-target species such as worms (Schmechel 2001). In addition, the displacement of juveniles during the harvesting process could affect subsequent populations (Anonymous 2011). Because hand-picking is the main method of collecting New Zealand Cockles, a score of 3 was awarded. Points of Adjustment (multiple selections allowed) Habitat for this species is so compromised from non-fishery impacts that the ability of the habitat to support this species is substantially reduced (e.g., dams; pollution; coastal development). New Zealand Cockles are found in soft mud to fine sand substrates (more common in sandier substrates), which occur on enclosed shores and protected beaches (MFish 2007a). Their habitat includes areas from the lowest high water neap tide mark to the lowest section of the shore but can also extend out to 20 m depth (MFish 2007a). Eelgrass beds are also home to New Zealand Cockles (MFish 2008). Due to their short siphons, they typically reside within the first 5 mm of sediment (Hewitt and Norkko 2006). Large concentrations are found in Otago Harbor, Waitati Inlet and Papanui Inlet (James et al. 2010). Habitat change has resulted in the loss of shellfish beds in New Zealand (Marsden and Adkins 2010). Increased sedimentation, land run-off, urban development and industrial contamination have been indicated in these losses (Morrison and Browne 1999). For example, New Zealand Cockle beds in Doubtful Sound, South Island showed reductions correlated with reductions in salinity that followed freshwater input from hydroelectric power stations (Tallis et al. 2004). In addition, New Zealand Cockles that are found in

8 estuaries appear to be under threat from anthropogenic changes and contaminants (Marsden and Adkins 2010). However, improvements in sewage treatment and discharge have been made over the past few decades and Cockles are now found in places they haven t been seen in for 50 years (Marsden and Adkins 2010). The ability of New Zealand Cockles to recolonize an area naturally after a disturbance varies greatly by site (Lundquist et al. 2009). For example, Lundquist et al. (2009) found that at sites with restricted dispersal of larvae, the larvae would mostly settle within the release location but few larvae from other sites would settle at this site. However, larvae from sites with high levels of connectivity could disperse to all other areas in a specific harbor and export of the larvae outside of the region was also high (Lundquist et al. 2009). We have subtracted points to account for the loss of shellfish habitat, despite some improvements over time Critical habitat areas (e.g., spawning areas) for this species are not protected by management using time/area closures, marine reserves, etc No efforts are being made to minimize damage from existing gear types OR new or modified gear is increasing habitat damage (e.g., fitting trawls with roller rigs or rockhopping gear; more robust gear for deep-sea fisheries) If gear impacts are substantial, resilience of affected habitats is very slow (e.g., deep water corals; rocky bottoms) Habitat for this species remains robust and viable and is capable of supporting this species Critical habitat areas (e.g., spawning areas) for this species are protected by management using time/area closures, marine reserves, etc. There are nine Marine Protected Areas and three Marine Parks in the Northeast region (MFish 2007a) and North west regions of New Zealand (MFish 2007b). There is a good likelihood that at least some of these MPAs and Parks provide protection for some New Zealand Cockle populations. For example, large beds of small New Zealand Cockles are found in the Motu Manawa Marine Reserve (Sivaguru and Grace 2001). However, these areas do not protect a large portion of New Zealand Cockles range so we have not added points Gear innovations are being implemented over a majority of the fishing area to minimize damage from gear types OR no innovations necessary because gear effects are minimal. Gear effects from hand picking are minimal and therefore gear innovations are not needed.

9 +0.25 If gear impacts are substantial, resilience of affected habitats is fast (e.g., mud or sandy bottoms) OR gear effects are minimal. Gear effects from hand picking are minimal and therefore gear innovations are not needed Points for Habitat Quality and Fishing Gear Impacts MANAGEMENT Core Points (only one selection allowed) Select the option that most accurately describes the current management of the fisheries of this species Regulations are ineffective (e.g., illegal fishing or overfishing is occurring) OR the fishery is unregulated (i.e., no control rules are in effect) Management measures are in place over a major portion over the species' range but implementation has not met conservation goals OR management measures are in place but have not been in place long enough to determine if they are likely to achieve conservation and sustainability goals. All aquatic life in New Zealand waters are managed through the Fisheries Act of 1996, which requires the Minister to keep populations above the level that can produce the maximum sustainable yield (MSY). Cockles are managed under the Quota Management System (QMS) (a total harvest limit must be set), and each population within the QMS is assigned to a Quota Management Area (QMA) and a Total Allowable Catch (TAC) is established for each of these QMAs (MFish 2007a). The Cockle fishery in Pakawau Beach is managed by the Challenger Shellfish Fishery Plan (MFish 2011b) and the North East Coast North Island Shellfish (FMA 1) Plan addresses Cockle fisheries (also under the QMS) in the northeast region (MFish 2011b). The West Coast North Island Shellfish plan manages Cockles in the west coast (MFish 2011b) and in the North West fisheries are managed under the North West Shellfish Plan, although currently there are no commercial New Zealand Cockle fisheries in this region (MFish 2007b). We have assigned a middle score because although management plans are in place, the actual population sizes are not known in several locations, suggesting there is a lack of information available.

10 3.00 Substantial management measures are in place over a large portion of the species range and have demonstrated success in achieving conservation and sustainability goals. Points of Adjustment (multiple selections allowed) There is inadequate scientific monitoring of stock status, catch or fishing effort. Catch and effort data from the Whangarei Harbor Cockle fishery have major issues that make them unusable (Williams et al. 2006) and biomass surveys have only been periodically undertaken in Snake Bank, Whangarei Harbor (Willims et al. 2006), Pakawau Beach, Ferry point and Tapu Bay (Osborne 2010) and in Papanui Inlet and Waitati Inlet (MFish 2008) Management does not explicitly address fishery effects on habitat, food webs, and ecosystems. New Zealand Cockle fishery management plans do not address fishery effects on habitat, food webs and ecosystems (eg. MFish 2007a) This species is overfished and no recovery plan or an ineffective recovery plan is in place Management has failed to reduce excess capacity in this fishery or implements subsidies that result in excess capacity in this fishery There is adequate scientific monitoring, analysis and interpretation of stock status, catch and fishing effort Management explicitly and effectively addresses fishery effects on habitat, food webs, and ecosystems This species is overfished and there is a recovery plan (including benchmarks, timetables and methods to evaluate success) in place that is showing signs of success OR recovery plan is not needed Management has taken action to control excess capacity or reduce subsidies that result in excess capacity OR no measures are necessary because fishery is not overcapitalized Points for Management

11 BYCATCH Core Points (only one selection allowed) Select the option that most accurately describes the current level of bycatch and the consequences that result from fishing this species. The term, "bycatch" used in this document excludes incidental catch of a species for which an adequate management framework exists. The terms, "endangered, threatened, or protected," used in this document refer to species status that is determined by national legislation such as the U.S. Endangered Species Act, the U.S. Marine Mammal Protection Act (or another nation's equivalent), the IUCN Red List, or a credible scientific body such as the American Fisheries Society Bycatch in this fishery is high (>100% of targeted landings), OR regularly includes a "threatened, endangered or protected species." 2.00 Bycatch in this fishery is moderate (10-99% of targeted landings) AND does not regularly include "threatened, endangered or protected species" OR level of bycatch is unknown Bycatch in this fishery is low (<10% of targeted landings) and does not regularly include "threatened, endangered or protected species." Interactions between the New Zealand Cockle fishery and protected species is not thought to occur (MFish 2007a) and the bycatch of other invertebrates during the harvest of New Zealand Cockles is low (Wilson et al. 1988). Points of Adjustment (multiple selections allowed) Bycatch in this fishery is a contributing factor to the decline of "threatened, endangered, or protected species" and no effective measures are being taken to reduce it Bycatch of targeted or non-targeted species (e.g., undersize individuals) in this fishery is high and no measures are being taken to reduce it Bycatch of this species (e.g., undersize individuals) in other fisheries is high OR bycatch of this species in other fisheries inhibits its recovery, and no measures are being taken to reduce it. Small New Zealand Cockles are typically discarded in this fishery, but it is suspected some of them survive (Osborn 2010). In addition, mortality of other New Zealand Cockles during the harvesting process is thought to be low (Bull 1984). However, there is no quantitative knowledge of other sources of mortality so we have not subtracted points (MFish 2009) The continued removal of the bycatch species contributes to its decline.

12 +0.25 Measures taken over a major portion of the species range have been shown to reduce bycatch of "threatened, endangered, or protected species" or bycatch rates are no longer deemed to affect the abundance of the "protected" bycatch species OR no measures needed because fishery is highly selective (e.g., harpoon; spear). Measures are not needed because interactions with protected species are not likely to occur There is bycatch of targeted (e.g., undersize individuals) or non-targeted species in this fishery and measures (e.g., gear modifications) have been implemented that have been shown to reduce bycatch over a large portion of the species range OR no measures are needed because fishery is highly selective (e.g., harpoon; spear). There is bycatch of other invertebrates, such as pipi s, in this fishery, but the levels of bycatch are thought to be low (Wilson et al. 1988) Bycatch of this species in other fisheries is low OR bycatch of this species in other fisheries inhibits its recovery, but effective measures are being taken to reduce it over a large portion of the range The continued removal of the bycatch species in the targeted fishery has had or will likely have little or no impact on populations of the bycatch species OR there are no significant bycatch concerns because the fishery is highly selective (e.g., harpoon; spear) Points for Bycatch REFERENCES Anonymous Reviewer Blue Ocean Institute New Zealand Cockle report. Bull, M A brief study of intertidal clam beds in Western Golden Bay associated with trials of a mechanical clam harvester. MAF Internal Report, 11 p. Baker, A.J The comparative biology of New Zealand oystercatchers. MSc thesis, University of Canterbury, Christchurch, New Zealand. Collie, J., Hall, S.J., Kaiser, M. and Poiner, I A quantitative analysis of fishing impacts on shelf-sea benthos. Journal of Animal Ecology 69: Cryer, M Assessment of cockles on Snake Bank, Whangarei Harbor, for New Zealand Fisheries Assessment Research Document 97/2. P. 29.

13 Cryer, M., Watson, T.G., Smith, M.D., MacKay, G., Tasker, R Biomass survey and stock assessment of cockles on Snake Bank, Whangarei Harbor, Draft New Zealand Fisheries Assessment Report submitted in fulfillment of project COC p. Dobbinson, S., J, Barker, M. & J.B. Jillett, Experimental shore level transplantation of the New Zealand cockle Chione stutchburyi. Journal of Shellfish Research 9: Dungan, C.F., Reece, K.S., Moss, J.A., Hamilton, R.M. and Diggles, B.K Perkinsus olseni in vitro isolates from the New Zealand clam Austrovenus stutchburyi. Journal of Eukaryot Microbiology 54: Hewitt, J, Norkko, J Incorporating temporal variability of stressors into studies: an example using suspension feeding bivalves and elevated suspended sediment concentrations. Journal of Experimental Marine Biology and Ecology 341: Irwin, C.R The impact of harvesting New Zealand littleneck clams (Austrovenus stutchburyi) and potential management options for a sustainable fishery. Proceedings of the 13th Biennial Coastal Zone Conference, July 13-17, 2003, Baltimore, MD. 3 p. James, M., Boyd, R. and Probert, K. 2010, Information on key species of interest to Ngai Tahu supplementary paper for next generation project. Port Otago ltd. 35 p. Leduc, D., Probert, P.K., Frew, R.D. and Hurd, C.L Macroinvertebrate diet in intertidal seagrass and sandflat communities: a study using C, N and S stable isotopes. New Zealand Journal of Marine and Freshwater Research 40: Lundquist, C.J., Oldman, J.W. and Lewis, M.J Predicting suitability of cockle Austrovenus stutchburyi restoration sites using hydrodynamic models of larval dispersal. New Zealand Journal of Marine and Freshwater Research 43: Marsden, I.D. and Adkins, S.C Current status of cockle bed restoration in New Zealand. Aquaculture International 18: Martin, N.D Chione stutchburyi population responses to exploitation. Unpublished MSc thesis, University of Auckland, New Zealand. Michael, K Community survey of cockles (Austrovenus stutchburyi) in Pauatahanui Inlet, Wellington, November NIWA client Report WLG p. Ministry of Fisheries (MFish). 2007a. Fisheries Plan North-East Shellfish. Ministry of Fisheries. Ministry of Fisheries. 28 p. Ministry of Fisheries (MFish). 2007b.. Fisheries Plan North-West Shellfish. Ministry of Fisheries. Ministry of Fisheries.10 p.

14 Ministry of Fisheries (MFish) Cockles (COC) (Austrovenus stutchburyi) Tuangi. Ministry of Fisheries. 3 p. Ministry of Fisheries (MFish). 2011a. Ministry of Fisheries (MFish). 2011b. Morrison, M.A. and Browne, G.N Intertidal shellfish population surveys in the Auckland region, , and associated yield estimates. NZ Fisheries Assessment Research Document 99/43. Morton, J., Miller, M The New Zealand she shore. Collins, Auckland. 653 p. Mouritsen, K.N The parasite-induced surfacing behavior in the cockle Austrovenus stutchburyi: a test of an alternative hypothesis and identification of potential mechanisms. Parasitology 124: Mouristen, k.n. and Poulin, R The risk of being at the top: foot cropping in the New Zealand cockle Austrovenus stutchburyi. Journal of Marine Biology 83: Mouritsen, K.N Intertidal facilitation and indirect effects: causes and consequences of crawling in the New Zealand cockle. Marine Ecological Progress Series 271: Osborne, T.A Biomass survey and stock assessment of the New Zealand littleneck clam (Chione stutchburyi) on Pakawau Beach, Golden Bay. Unpublished report prepared for Westhaven Shellfish Co. Ltd. 27 p. Osborne, T.A biomass survey and stock assessment of the New Zealand littleneck clam (Chione stutchburyi) on Pakawau Beach, Golden Bay. Unpublished report prepared by Osborne Research Co. Ltd. For Westhaven Shellfish Co. Ltd. 15 p. Osborne, T.A Biomass survey and stock assessment of cockles (Austrovenus stutchburyi) in area COC7A: Tapu Bay, Ferry Point and Pakawau. New Zealand Fisheries Assessment Report 2010/44. Owen, S.J A biological powerhouse: the ecology of the Avon-Heathcote Estuary, pp In: S.J. Owen (ed) The estuary: where our rivers meet the sea. Parks Unit, Christchurch City Council, Christchurch. Schmechel, F Potential impacts of mechanical cockle harvesting on shorebirds in Golden and Tasman Bays, New Zealand. DOS Science Internal Series p. Sivaguru, K. and Grace, R Benthos and sediments of Motu Manawa (Pollen Island) Marine Reserves. Auckland Conservancy, Newton, Auckland. 24 p.

15 Stewart, M.J Ecological effects associated with urban development on populations of the New Zealand cockle (Austrovenus stutchburyi). PhD thesis, University of Auckland. Tallis, H.M., Wing, S.R.,and Frew, R.D Historical evidence for habitat conversion and local population decline in a New Zealand fjord. Ecological Applications 14: Thomas, E. and Poulin, R Manipulation of a mollusk by a trophically transmitted parasite: convergent evolution or phylogenetic inheritance: Parasitology 116: Williams, J.R., Cryer, M., McKenzie, J.R., Smith, M.D., Watson, T.G., MacKay, G., and Tasker, R Biomass survey and stock assessment of cockles (Austrovenus stutchburyi) on Snake Bank, Whangarei Harbor, Wilson, N., Stevens, J., Alspach, P. and Butler, D Environmental impact assessment, effects of mechanical harvesting of cockles from the Pakawau/Puponga intertidal area. Report prepared by Department of Scientific and Industrial Research (DSIR), Division of Horticulture and Processing, Fish Technology Section, Nelson, for Westhaven Shellfish Co., Ltd.