Reinstatement of customary seabird harvests after a 50-year moratorium

Abstract

Seabird eggs, chicks, and adults have significant value for many cultures, but delayed maturation, low reproductive rates, and ease of exploitation at breeding colonies make these species especially vulnerable to overharvest. In New Zealand, indigenous Māori placed a moratorium over the harvest of greyfaced petrel (Pterodroma gouldi) chicks in the 1960s because of concerns about diminished returns. Over the last decade, those tribes have indicated their desire to reinstate a small customary harvest. We used recent estimates of population sizes and demographic parameters to develop population models to investigate the feasibility of reinstating a sustainable harvest of pre-fledgling chicks from 2 island populations: Moutohorā and the Ruamāhua Islands. In the absence of harvest, our simulations predicted mean annual rates of population growth of 1.01 (95% CI 1.010-1.014) for the colony on Moutohorā and 0.983 (0.978-0.989) for the Ruamāhua Islands. The Moutohorā colony could potentially sustain a fixed-quota harvest of up to 6,000 chicks or a fixed-proportion harvest of up to 30% of chicks, annually. A larger-scale harvest would require either a very conservative fixed-quota harvest with strict monitoring of bag limits, or a fixed-proportion harvest with reliable ongoing monitoring of the population size. We propose that Māori authorities use a fixed-quota system up until they develop and use either a scientific assessment or a harvester-derived index of population change. On the basis of our simulations, in 2010, Ngāti Awa, the local tribe, harvested chicks from Moutohorā for the first time in half a century. Ó 2014 The Wildlife Society.

Māori traditional harvest, knowledge and management of sooty shearwaters (Puffinus griseus) in the Marlborough Sounds, New Zealand

“…Traditional harvest, even of very few birds, is crucial to maintaining connections between iwi, sooty shearwaters and mātauranga Māori, and to Māori reasserting mana (prestige) and rangatiratanga (chieftainship) over the resource (Gaze & Smith 2009;Lyver et al 2008b). Ngāti Kuia have already resumed such a harvest for sooty shearwaters on Tītī Island (Gaze & Smith 2009), as have Ngāti Awa for the grey-faced petrel (Pterodroma gouldi) in New Zealand's Bay of Plenty (Jones et al 2015). The inclusion of mātauranga Māori in the management of these and other petrel customary harvests (Lyver et al 2008b;Moller et al 2004) will enable the persistence of important cultural practices, reduce poaching, and provide a means for monitoring populations of this culturally important seabird.…”

Insights to the functional relationships of Māori harvest practices: Customary use of a burrowing seabird

“…The lack of long-term species-specific data linking fledging mass to subsequent probability of recruitment, however, meant that we could not model the influence of these demographic parameters on growth rates as part of this study. We emphasize that our deterministic modeling exercise addresses the relative effects of harvest practices on population growth rates, and our results are not therefore quantitative, probabilistic predictions of safe harvest limits under stochastic environmental conditions (Jones et al 2015a). Although our results suggest that the practices were defensible biologically, adjusting and accounting for environmental variability also requires a flexible harvest management system.…”

“…We emphasize that our deterministic modeling exercise addresses the relative effects of harvest practices on population growth rates, and our results are not therefore quantitative, probabilistic predictions of safe harvest limits under stochastic environmental conditions (Jones et al a ). Although our results suggest that the practices were defensible biologically, adjusting and accounting for environmental variability also requires a flexible harvest management system.…”

“…The New Zealand population of grey-faced petrels is estimated to be 1 million breeding and non-breeding individuals (Taylor 2000). We chose this as a focal species because a range of associated customary practices have developed over its many generations of harvest (Lyver et al 2008) and it has been the subject of recent studies (Jones et al 2011(Jones et al , 2015aWhitehead et al 2014); therefore, estimates of the demographic parameters required for population modeling are available (see Table 1 in Jones et al 2015a).…”

“…A deterministic approach was appropriate because our main purpose was to explore and compare the relative effects of historical customary practices on a common metric; in this case, annual population growth rate, l (Heppell et al 2000a, b;Beissinger et al 2006) and not to predict, quantitatively, likely future population changes. For a detailed examination of contemporary harvest strategies in a stochastic environment, we direct readers to Jones et al (2015a). We based our modeled population on a simplified life cycle (see Fig.…”