Chris Lalas

Folklore and chimerical numbers: Review of a millennium of interaction between fur seals and humans in the New Zealand region

Abstract The increase in numbers and range expansion of New Zealand fur seals (Arctocephalus forsteri Lesson) in the New Zealand region has prompted many people to comment on their effects on the marine and coastal environments. Overall there are anomalies in the data describing the distribution and abundance of fur seals in the New Zealand region, and there is a need for a better understanding of the interactions with humans and the impacts on the New Zealand environment. The distribution resulting from the present pattern of re‐colonisation differs from the perception of their distribution before decimation by humans. We hypothesise that the pristine distribution was temperate rather than subantarctic. Previously published records which have documented changes in the abundance and distribution of the species are shown to be wanting. The most controversial management issue is interaction with commercial fisheries where we conclude that neither of the extreme options, culling of seals nor closure of some fishing grounds, is justified. Other issues addressed include tourism, te tikanga Maori o mahinga kai (the customary use of wildlife by Maori), and impact of fur seals on the coastal environment. This species offers a rare and exciting opportunity to test the theoretical processes of population expansion that can be investigated as a natural experiment. We suggest that the current management policy should remain unchanged until the current paucity of information on the degree of interaction between fur seals and humans has been addressed.

Pup production of the New Zealand fur seal on Otago Peninsula, New Zealand

The New Zealand fur seal (Arctocephalus forsteri) did not breed in Otago, southeastern South Island, New Zealand from the 17th Century until the late 1970s. Here we report a recent dramatic increase in pup production for Otago Peninsula, from 20–30 pups born in two rookeries in 1982/83 to a minimum (from a direct count) of 673 born at eleven distinct rookeries during the 1993/94 breeding season. Adjustments for precensus mortality and for undercounting were calculated from one site and applied to all rookeries. These adjustments raised the 1993/94 production figure to an estimated 1136 ± 98 pups. The implications of these adjustments, and of making pup counts based on surveys, are discussed. Future monitoring of pup numbers should be carefully timed to coincide with the end of the local pupping season.

Expectations for population growth at new breeding locations for the vulnerable New Zealand sea lion (Phocarctos hookeri) using a simulation model

Management plans for threatened or recovering large vertebrate species that are increasing in population size and range focus on the establishment of viable populations within set temporal limits.New Zealand (Hookers) sea lions ( Phocarctos hookeri) were declared a threatened species in 1997, and New Zealand legislation requires that threatened species of marine mammals must be managed to reduce human-induced mortality and achieve a non-threatened status within 20 years.The present breeding distribution of P. hookeri is highly localised, with over 95% of total annual pup production located at Auckland Islands and almost all of the remainder at Campbell Island.Breeding elsewhere has been ephemeral or restricted to < 10 adult females.The only recorded sustainable breeding at a new location has been at Otago, South Island, New Zealand.This breeding population consisted of a total of four breeding females in 2002 and is derived from one immigrant female that gave birth to her first pup in the 1993/1994 breeding season.The New Zealand Department of Conservation management plan specifies that to achieve a non-threatened status P. hookeri (1) at Otago must increase in the number of breeding females to 510, and (2) must establish 5two new breeding locations within the 20-year time frame, each with 510 breeding females.This study 1) projects the population growth trends at a new location (Otago) to see if it will achieve 510 breeding females within the legislated time frame, and (2) examines the likelihood that other breeding locations will establish elsewhere given the demographic information available for this species.We present 20 deterministic and three stochastic Leslie matrix model scenarios for female population growth for the initial years following the start of breeding at a new location.Our results indicate that (1) a new breeding population derived from one immigrant female is unlikely to reach 10 breeding females in 20 years; this duration is more likely to be 23–41 years (deterministic models) or 23–26 years (stochastic model), (2) the likelihood of two new sites establishing within 20 years is unquantifiable, but the probability is low, and (3) if the legislated outcome and time limit are not revised in the population management plan, the feasibility and effectiveness of re-locating young females could be investigated. # 2003 Elsevier Ltd.All rights reserved.

Moult and changes in body shape and pelage in known‐age male New Zealand sea lions (Phocarctos hookeri)

Abstract We observed a small population of male New Zealand sea lions (Phocarctos hookeri) in 7 consecutive years at Otago, New Zealand, a region north of the main breeding population. Changes in pelage, body shape, and body length, with growth of tagged, known‐age males were used to define age class categories: “juvenile” (1–3 years), “subadult” (4–5 years) and “adult” (6 years and older). Accurate assessments of age are important to determine immigration rates of cohorts into a small population. We used photographic identification to recognise individuals so that the progression of moult could be determined. Individuals 2+ years old underwent a complete annual moult over a period of c. 2 months between December and June. Juveniles moulted earlier than subadults and adults. However, 1‐year‐old males underwent only a partial annual moult. Knowledge of the timing of moult is important for the deployment of remote sensing devices glued to the pelage, because moult will result in the loss of attached equipment.

New Zealand sea lion predation on New Zealand fur seals

Abstract Several sea lion species are known to occasionally hunt fur seals for food, but there have been few reports of New Zealand (Hookers) sea lions {Phocarctos hookeri) hunting and eating New Zealand fur seals (Arctocephalus forsteri) We describe the first reported incidence of P. hookeri eating A. forsteri pups in mainland New Zealand, and present evidence suggesting that it was active predation rather than scavenging. In late April, early May, and early September 1997 we found three sea lion regurgitations containing the remains of fur seal pups on Otago Peninsula, New Zealand. One contained three plastic tags formerly placed on three different female fur seal pups from a nearby breeding colony. When ingested at least two of the three identifiable pups fell within the lower condition quartile calculated from pups at their natal colony. The incidence of such predation may increase with increasing densities of both fur seals and sea lions in Otago, but the impact on the trends in fur seal populations...

Geographically contrasting biodiversity reductions in a widespread New Zealand seabird

Unravelling prehistoric anthropogenic impacts on biodiversity represents a key challenge for biologists and archaeologists. New Zealands endemic Stewart Island Shag (Leucocarbo chalconotus) comprises two distinct phylogeographic lineages, currently restricted to the countrys south and southeast. However, fossil and archaeological remains suggest a far more widespread distribution at the time of Polynesian settlement ca. 1280 AD, encompassing much of coastal South Island. We used modern and ancient DNA, radiocarbon dating, and Bayesian modelling, to assess the impacts of human arrival on this taxon. Our analyses show that the southeast South Island (Otago) lineage was formerly widespread across coastal South Island, but experienced dramatic population extinctions, range retraction and lineage loss soon after human arrival. By comparison, the southernmost (Foveaux Strait) lineage has experienced a relatively stable demographic and biogeographic history since human arrival, retaining much of its mitochondrial diversity. Archaeological data suggest that these contrasting demographic histories (retraction vs. stability) reflect differential human impacts in mainland South Island vs. Foveaux Strait, highlighting the importance of testing for temporal and spatial variation in human‐driven faunal declines.

Strong Phylogeographic Structure in a Sedentary Seabird, the Stewart Island Shag (Leucocarbo chalconotus)

New Zealands endemic Stewart Island Shag (Leucocarbo chalconotus) comprises two regional groups (Otago and Foveaux Strait) that show consistent differentiation in relative frequencies of pied versus dark-bronze morphotypes, the extent of facial carunculation, body size and breeding time. We used modern and ancient DNA (mitochondrial DNA control region one), and morphometric approaches to investigate the phylogeography and taxonomy of L. chalconotus and its closely related sister species, the endemic Chatham Island Shag (L. onslowi). Our analysis shows Leucocarbo shags in southern New Zealand comprise two well-supported clades, each containing both pied and dark-bronze morphs. However, the combined monophyly of these populations is not supported, with the L. chalconotus Otago lineage sister to L. onslowi. Morphometric analysis indicates that Leucocarbo shags from Otago are larger on average than those from Foveaux Strait. Principal co-ordinate analysis of morphometric data showed substantial morphological differentiation between the Otago and Foveaux Strait clades, and L. onslowi. The phylogeographic partitioning detected within L. chalconotus is marked, and such strong structure is rare for phalacrocoracid species. Our phylogenetic results, together with consistent differences in relative proportions of plumage morphs and facial carunculation, and concordant differentiation in body size and breeding time, suggest several alternative evolutionary hypotheses that require further investigation to determine the level of taxonomic distinctiveness that best represents the L. chalconotus Otago and Foveaux Strait clades.

Autumn diet of recolonising female New Zealand sea lions based at Otago Peninsula, South Island, New Zealand

New Zealand (NZ) sea lions (Phocarctos hookeri) are slowly recolonising the Otago coast, South Island, New Zealand. The increase in their numbers may lead to resource competition with other marine predators and fisheries. We determined the diet of female NZ sea lions at Otago during autumn. In total, 571 scats and 110 regurgitations were collected on Otago Peninsula during 2008 and 2009. Barracouta (Thyrsites atun) and jack mackerel (Trachurus sp.) were the two main prey species and accounted for 26% and 31% of the reconstituted biomass, respectively. This was consistent between two years. Only five other species contributed > 5% of the diet by biomass in either year. Prey species are all found on the narrow continental shelf surrounding Otago Peninsula. The main prey species of Otago NZ sea lions may be of higher energy content than prey in the Auckland Islands (remnant breeding area). Resource overlap with other marine predators and fisheries appears to occur around Otago Peninsula. A marine trophic model of the area off Otago Peninsula would help understanding potential competition between marine predators and fisheries in this area.

Estimates of size for the large octopus Macroctopus maorum from measures of beaks in prey remains

Abstract Macroctopus maorum, also known as Octopus maorum and Pinnoctopus cordiformis, grows to 12 kg and is the largest octopod in Australasia. In New Zealand, this species features in the diets of seals and albatrosses. Beaks of depredated octopus resist digestion and accumulate in the stomach until regurgitated or defecated. Beaks of M. maorum were differentiated reliably from those of other octopods in prey remains for octopus > c.100 g. Previous studies estimated the size of depredated M. maorum from measures of lower beaks using equations derived either from a small sample of M. maorum or from related species. Here, allometric equations to estimate ventral mantle length (4.6–27.5 cm), dorsal mantle length (5.1–29.0 cm), total length (20–198 cm), and body mass (36–12 000 g) were derived from measures of both upper and lower beaks of 90 specimens of M. maorum. These regressions were imprecise and reflected innate variability in octopus morphometrics, a characteristic reflected in the results of analyses of published data for M. maorum from northern New Zealand and for two other large octopods, Octopus vulgaris and Enteroctopus magnificus.

Diet composition, continuity in prey availability and marine habitat – keystones to population stability in the Snares Penguin (Eudyptes robustus)

Abstract Worldwide, crested penguins (Eudyptes spp.) are in decline and it is suspected that reduced prey availability plays an important role. However, the population of Snares Penguins (E. robustus) does not follow this trend, with its population being stable if not slightly increasing. To assess whether the success of the Snares Penguins is a result of a rich and stable prey resource within the breeding range of the species, we examined the dietary composition of breeding Snares Penguins by analysis of stomach contents, and analysed ratios of carbon (δ13C) and nitrogen (δ15N) stable isotopes in feathers of living penguins and historical specimens. The food brought ashore by the Penguins was dominated by a single species of krill, Nyctiphanes australis (∼60% of wet weight of the stomach samples); fish (∼30%) and cephalopods (∼10%) seemed to form only a minor portion. However, numbers of fish otoliths and cephalopod beaks in the samples suggest that these prey classes are more important food source for adult Penguins while at sea. Stable isotope ratios of Snares Penguin feathers collected between 1880 and 2004 revealed no temporal trend in either δ13C or δ15N indicating no significant changes in marine productivity or general composition of the diet of Snares Penguins in the past 120 years. We discuss our findings in the light of declining population trends and changing stable isotope ratios recently detected in Rockhopper Penguins (E. chrysocome), and conclude that the Snares Penguins benefit from stable prey availability as a function of the oceanographic setting of their breeding habitat.