The biology, ecology and history of toheroa (Paphies ventricosa): a review of scientific, local and customary knowledge

Figures & data

Figure 1. Distribution of toheroa (Paphies ventricosa) in New Zealand. Major populations are underlined. Figure reproduced from Redfearn (1974).

Table 1. Summary of factors considered to potentially be preventing the recovery of toheroa, the mechanisms by which these factors might affect toheroa recovery, possible management actions to address factors and relevant toheroa literature.

Factors that may be preventing the recovery of toheroa	Possible mechanism(s)	Management actions to address effects			Relevant toheroa literature and research
		Past	Present	Possible future options
Climate and weather	Changes in food availability; frequency of stranding events; beach morphology, sand smothering or beach instability	–	–	Adjust customary harvest to account for environment-driven population variation	Williams, Sim-Smith, et al. (2013), Cassie (1955)
Toxic algal blooms (TAB)	Mortality via smothering and anoxia	–	–	Adjust customary harvest to account for population variation as a consequence of TAB related mortality	Williams, Sim-Smith, et al. (2013)
Disease	Mortality events; effects on health, growth or reproduction	Avoid harvesting (or survey) practises that damage unharvested animals or involve the processing of toheroa, or discarding of their waste, on the beach or near a toheroa bed	Avoid harvesting (or survey) practises that damage unharvested animals or involve the processing of toheroa, or discarding of their waste, on the beach or near a toheroa bed (not practised by all harvesters and researchers)	Adjust customary harvest to account for population variation as a consequence of disease and mortality events; Manage translocations of toheroa and other species to reduce risk of spreading disease to uninfected locations	Ross et al. (2017)
Recruitment limitation	Levels of recruitment may be insufficient to facilitate recovery of toheroa populations	Māori may have preferentially harvested middle sized toheroa leaving larger individuals in place as broodstock to sustain the resource; Tikanga around foot traffic on upper beach provided protection for both the nursery habitat and the vulnerable early life stages of toheroa; Translocation of toheroa to supplement existing populations or establish new ones; Tikanga around cessation of harvesting during main spawning periods which was indicated by the annual flowering of kumarahou (Pomaderris kumarahou) and the full moon; Use of rāhui to set aside beds and spawning areas; Commercial fishery at Ripiro transplanted large toheroa to the southern end of Pouto Peninsula, to act as a source of recruits to beds to the north	Translocation of toheroa to supplement existing populations or establish new ones. Contemporary translocations are at present being conducted both with and without permits	Spat production and reseeding or translocation of adults where populations demonstrated to be recruit limited; Management of vehicle activity during recruitment season to maximise survival of spatfall	Newcombe et al. (2015), Williams, Ferguson, et al. (2013), Beentjes (2010a), Beentjes (2010b), Moller et al. (2009b), Williams (2004), Smith (2003), Minister of Marine (1933), Parore (1933)
Vehicle activity	Direct crushing, increased desiccation risk, or increased predation risk from birds, reduced stability	–	Adjustments to location of annual beach motorcycle race at Oreti to minimise impacts on toheroa	Driver education to modify behaviour and use of vehicles on beaches; Spatial and/or temporal closures of beaches to vehicles Insertion of physical barriers as a way of modifying vehicles activity	Moller et al. (2009b), Hooker and Redfearn (1998), Brunton (1978), Redfearn (1974)
Changes in land use	Changes in flow of freshwater to coast; degradation of water quality; changes in beach morphology; beach erosion and loss of habitat	–	–	Modify land use to minimise impacts on (or restore) toheroa habitat and ecology	Williams, Sim-Smith, et al. (2013), Smith (2013), Beentjes et al. (2006), Akroyd (2002)
Human harvesting	Harvesting at an unsustainable level or at levels that do not allow populations to recover; incidental mortality of non-harvested toheroa	Allocation of lease areas for commercial harvesting Minimum size, daily bag limit, harvest method, season and area restrictions for recreational fishery; Rotational harvest of toheroa beds and ‘thinning’ of selected high density beds by customary fishers; Cessation of harvesting effort by customary fishers around known times of major spawning events	Closure of commercial and recreational fisheries; Creation of customary harvest system	Improvements to customary harvest system; Allocation of resources to improve enforcement of fisheries regulations; Education and community engagement to inform customary harvest, reduce illegal harvesting, and assist enforcement of regulations through peer pressure and reporting of illegal harvest	Miskelly (2016), Akroyd et al. (2008), Smith (2013), Redfearn (1974)
Natural predation by birds, fish or invertebrates	Predation at an unsustainable level or at levels that do not allow populations to recover	Collection or destruction of black-backed gull (Larus dominicanus) eggs by locals from breeding rookeries located among cliffs above toheroa beds	–	Management of bird populations if/where links to toheroa population failure are proven	Brunton (1978)

Figure 2. (Clockwise from top left) Toheroa collected from Hokio Beach during the September open day in 1977 (EP/1077/3679/36-F. Alexander Turnbull Library (ATL)); Three women from Northland, photographed ca. 1910–1930s, shelling toheroa meat into tin cans for a toheroa cannery. Their kete (flax bags) are full of shellfish, and they are surrounded by empty shells (1/1-026522-G. ATL); Harvesting toheroa on a Northland beach, ca. 1920s–1930s (1/1-010575-G. ATL); Toheroa being dug from trenches on Muriwai Beach, 1962. (AAQT 6539, A70987. Archives New Zealand, The Department of Internal Affairs, Te Tari Taiwhenua).

Figure 3. Total commercial production of toheroa (Paphies ventricosa; tonnes of canned toheroa product) from canneries at Northland Beaches (Te Oneroa-a-Tōhē, Ripiro and Te Rangatira) from 1928 to 1969. Data from Marine Department Annual records for 1928–1940 and 1943–1948 tabulated by Cassie (1955) and for 1941–1942 and 1949–1969 graphed by Redfearn (1974). Figure reproduced from Williams, Sim-Smith, et al. (2013).

Figure 4. Population estimates of large adult toheroa (Paphies ventricosa) at Te Oneroa-a-Tōhē (≥75 mm; 1933–2010), Ripiro (≥ 75 mm; 1938–2011), Oreti (≥80 mm and ≥100 mm; 1972–2009) and Bluecliffs Beach (≥75 mm and ≥ 100 mm; 1966–2009) from 1930 to 2015. Figures reproduced from Williams, Ferguson, et al. (2013), Beentjes (2010a, 2010b) and Berkenbusch et al. (2015).

Figure 5. Internal anatomy of toheroa (Paphies ventricosa), with left valve and mantle removed. Figure reproduced from Rapson (1952).

Figure 6. Left valves of toheroa (Paphies ventricosa) shells collected at Ripiro (153 mm), Oreti (108 mm) and Mt Maunganui (70 mm) beaches.

Figure 7. Length-frequency distribution of toheroa sampled during the 2009 at Oreti (n = 1221; Beentjes 2010b) and in 2011 survey at Ripiro (n = 7578, Williams, Ferguson, et al. 2013).

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