Academic literature on the topic 'Eudyptes robustus'

The designation of Marine Protected Areas has become an important approach to conserving marine ecosystems that relies on robust information on the spatial distribution of biodiversity. We used GPS tracking data to identify marine Important Bird and Biodiversity Areas (IBAs) for the Endangered northern rockhopper penguin Eudyptes moseleyi within the Exclusive Economic Zone (EEZ) of Tristan da Cunha in the South Atlantic. Penguins were tracked throughout their breeding season from 3 of the 4 main islands in the Tristan da Cunha group. Foraging trips remained largely within the EEZ, with the exception of those from Gough Island during the incubation stage. We found substantial variability in trip duration and foraging range among breeding stages and islands, consistent use of areas among years and spatial segregation of the areas used by neighbouring islands. For colonies with no or insufficient tracking data, we defined marine IBAs based on the mean maximum foraging range and merged the areas identified to propose IBAs around the Tristan da Cunha archipelago and Gough Island. The 2 proposed marine IBAs encompass 2% of Tristan da Cunha’s EEZ, and are used by all northern rockhopper penguins breeding in the Tristan da Cunha group, representing ~90% of the global population. Currently, one of the main threats to northern rockhopper penguins within the Tristan da Cunha EEZ is marine pollution from shipping, and the risk of this would be reduced by declaring waters within 50 nautical miles of the coast as ‘areas to be avoided’.

Seabirds have become adapted for foraging in an oceanic environment that can be highly dynamic. Oceanographic processes determine the spatial distribution of seabird prey, while seasonality often has a temporal influence on prey availability. In penguins, these factors are reflected in the different species� foraging strategies. Penguins can broadly be categorized as inshore foragers that live in subtropical to temperate regions and profit from a stable food supply throughout the year close to their breeding sites, and offshore foragers that breed in a pelagic environment at higher latitudes where oceanographic processes and seasonality create much more dynamic, temporally limited prey situations. In this light, offshore foragers can be expected to be much more flexible in their foraging behaviour so as to quickly respond to changes in a dynamic marine environment, while inshore foragers are more likely to exhibit predictable foraging patterns. I examined the foraging ecology of two New Zealand penguin species - the offshore foraging Snares penguin Eudyptes robustus and the inshore foraging Yellow-eyed penguin Megadyptes antipodes and how their foraging strategies reflect an adaptation to the marine environment they exploit. Diet composition of breeding Snares penguins (incubation and early chick-guard) was determined using the water-offloading method. Before the chicks hatched, the penguins generally brought little food back from their long foraging trips. During chick-guard, the stomach contents comprised mainly of crustaceans (~55%), fish (~24%) and cephalopods (~21%). However, the presence at times of many fish otoliths and squid beaks suggests that the latter two prey classes may play an even more important role in the adults� diet than the simple percentages based on mass suggest. The penguins� nesting routines were strongly synchronised between the years and correlated with the onset of the spring planktonic bloom. Using GPS data loggers and dive recorders I found that during the incubation phase, male penguins that performed long (ca. 2 week) foraging trips exhibited a strong affinity to forage in the Subtropical Front some 200 km east of the Snares. At that stage (late mid-October) the front featured elevated chlorophyll a concentrations, a pattern that can be observed every year. Thus, it seems that the front represents a reliable and predictable source of food for the male penguins. After the males returned, the female penguins also performed long foraging trips (<1 week) but never reached the front, primarily because they had to time their return to the hatching of their chicks. After the chicks had hatched, the female Snares penguins were the sole providers of food. At this stage, the penguins performed short foraging trips (1-3 days) and foraged halfway between the Snares and Stewart Island (ca. 70-90 km north of the Snares), where nutrient-rich coastal waters flow eastwards to form the Southland Current. The penguins concentrated their diving effort in these waters, underlining the importance of the warm coastal waters as a food source for breeding Snares penguins. However, diving behaviour between 2003 and 2004 differed with penguins searching for prey at greater depths in the latter year. This underlines the Snares penguins� behavioural flexibility in response to a changing marine environment. The Yellow-eyed penguins as typical inshore foragers showed very consistent foraging patterns at all stages. GPS logger deployments on penguins at Oamaru revealed that the birds foraged almost exclusively at the seafloor and targeted specific areas that featured reefs or epibenthic communities. As a result, the penguins� at-sea movements appeared conservative and at times almost stereotypic. Nevertheless, a comparison of Yellow-eyed penguins breeding on the adjacent Codfish and Stewart islands revealed a degree of plasticity in the species� foraging behaviour. Birds from Codfish Island extended their foraging ranges considerably and switched from primarily bottom to mid-water foraging during the post-guard stage of breeding. It seems likely that this switch is a result of enhanced feeding conditions (e.g. increased prey abundance/quality) in an area further away from the island, but the time required to get there renders this strategy not viable when chicks are small and need to be guarded and fed on a daily basis. As such, the change of behaviour represents a traditional pattern rather than a dynamic response to a sudden change in the marine environment. In comparison, penguins from Stewart Island showed consistent foraging patterns during all stages of breeding. Given the high levels of chick starvation on Stewart Island, the lack of plasticity in foraging behaviour is surprising and might indicate that Yellow-eyed penguins find it difficult to react quickly to a sub-optimal food situation. Overall, it seems that Yellow-eyed penguins show a specialisation for a consistent benthic environment and, thus, lack the behavioural flexibility apparent in Snares penguins, which find their food in a changing pelagic marine environment.

Dissertação de Mestrado em Ecologia apresentada à Faculdade de Ciências e Tecnologia
No Oceano Austral, os cefalópodes têm um papel muito importante nas redes tróficas onde os pinguins se alimentam deles. O pinguim das Snares, Eudyptes robustus, é uma espécie endémica das Ilhas das Snares, Nova Zelândia. Estes foram usados como amostradores biológicos para avaliar a componente de cefalópodes na sua dieta na região das Ilhas Snares e para avaliar o tipo de habitat e nível trófico que os cefalópodes ocupam (através de análise de isótopos estáveis dos bicos). O pinguim das Snares está classificado como “vulnerável” de acordo com a Conservação da Natureza e dos Recursos Naturais (IUCN), devido ao facto de terem um habitat restrito e serem suscetíveis a atividades antropogénicas. Dados da dieta desta espécie são historicamente escassos e, como tal, procedi a uma análise detalhada da sua dieta durante o período reprodutor de 1986/87 (Novembro a Fevereiro). Os resultados demonstraram que se alimenta de três espécies diferentes de cefalópodes (Nototodarus sloanii, Onykia ingens, e Octopus campbelli) (998, 1221 e 294 bicos, respetivamente, de 36 amostras). Todos os indíviduos das três espécies eram juvenis, mas os de N. sloanii (tamanho médio do manto (ML) = 128.9 mm; massa média (M) = 63.7 g) eram maiores que os de O. ingens (ML = 73.9 mm; M = 23.6 g) e maiores que os de O. campbelli (ML = 0.4 mm; M = 0.6 g). Pela frequência de ocurrência e massa, N. sloanii foi a espécie mais importante (F% = 97.2; M% = 72.5) e O. ingens a mais importante em número (N% = 48.6). Mattern, et al. (2009) descreveu uma alta diversidade de cefalópodes na dieta de pinguins das Snares nas amostras recolhidas no período reprodutor de 2002, de Outubro a Novembro (N = 11 taxa versus 3 espécies no meu estudo). As espécies mais importantes em ambos os estudos foram as mesmas (N. sloanii e O. ingens). É de frisar que Mattern, et al. (2009) descreveu a presença de Histioteuthis atlantica, lula associada a águas quentes, e a presença da espécie pelágica de polvo Ocythoe tuberculata, ambos numericamente relevantes. Estes resultados sugerem que os pinguins das Snares talvez procuraram o seu alimento em águas mais pelágicas nos anos 2000 do que na década de 80. Através da análise de isótopos estáveis, o meu estudo demonstrou que as espécies, N. sloanii e O. ingens, ocupavam um habitat similar (média δ13C ± SD; -17.8 ± 0.2, -17.4 ± 0.5, respetivamente) na plataforma continental das Ilhas das Snares, mas a espécie de polvo O. campbelli ocupava um habitat mais a sul (-18.5 ± 0.3). Além disso, O. campbelli consumiu presas de nível trófico mais elevado (média δ15N ± SD; 6.7 ± 0.5) quando comparado com as espécies de lula N. sloanii e O. ingens (4.8 ± 0.9, 4.3 ± 0.9, respetivamente). O. campbelli é uma espécie de polvo bêntica e, num sistema bêntico de reciclagem de nutrientes, este é tipicamente melhorado sendo traduzido em elevados valores de δ15N na base da cadeia trófica.As espécies de cefalópodes O. ingens e O. campbelli foram ambas descritas na dieta de pinguins das Snares, assim como na dieta de pinguins Eastern Rockhopper (Eudyptes chrysocome filholi) (Ilhas Campbell). Os valores de δ13C de O. ingens diminuiram de -17.6 ± 0.5 (Ilhas Snares) para -18.8 ± 0.8 (Ilhas Campbell, mais a sul), sugerindo que estes indivíduos não eram da mesma população. Comparando os valores de δ13C de O. campbelli (-18.5 ± 0.3) das Ilhas Snares com os valores das Ilhas Campbell (-18.8 ± 0.6), estes indivíduos eram provavelmente da mesma população, sugerindo que os pinguins das Snares talvez tivessem procurado as suas presas mais a sul em águas Sub-Antárticas próximas da Ilha de Campbell. Quanto ao nível trófico (δ15N) de O. ingens, esta lula predada por pinguins das Snares (4.3 ± 0.9) teve um nível trófico idêntico ao da lula O. ingens predada pelos pinguins Eastern Rockhopper (4.4 ± 0.6). Isto sugere que ambos os indivíduos tinham dietas similares. O nível trófico de O. campbelli consumido por pinguins das Snares apresentou valores mais elevados (6.7 ± 0.5) quando comparados aos pinguins Eastern Rockhopper (4.4 ± 0.8), inferindo que provavelmente estes indivíduos de O. campbelli tinham dietas diferentes.Em relação às pescas locais de cefalópodes, a lula N. sloanii já era alvo de pescas comerciais na década de 80 na plataforma continental das Snares, onde indivíduos de tamanho maior (ML: 150-386 mm) eram pescados em comparação àqueles que foram descritos na dieta dos pinguins das Snares, mesmo que haja uma sobreposição das áreas de pesca e nas áreas de forrageamento dos pinguins das Snares. Desde os anos 80, as pescas locais ocurrem durante o período reprodutivo dos pinguins das Snares, mas como estes só se reproduzem nas Ilhas das Snares, a 200 km a sul da Nova Zelândia, o risco desta espécie interagir com pescas é baixo quando comparado com outras espécies de pinguim, embora não deva ser menosprezado. Mais, as alterações climáticas podem vir afetar a disponibilidade de presas, incluindo cefalópodes, tornando-se numa ameaça real num futuro próximo.
In the Southern Ocean and adjacent waters, cephalopods play an important role in food webs where penguins are known to feed considerably on them. The Snares penguin, Eudyptes robustus, an endemic penguin species from Snares Islands, New Zealand, was used as a biological sampler to evaluate the cephalopod component of the diet of penguins around the Snares Islands and assess the habitat and trophic level of cephalopods (through stable isotope analyses of beak material). Snares penguin is classified as “vulnerable” according to the International Union for Conservation of Nature (IUCN) due to its restricted habitat and susceptibility to anthropogenic activities. As historical diet data is rare for this species, I carried out detailed analyses of the diet of Snares penguins in the breeding season 1986-87 (Nov.-Feb.). The results show that penguins feed on three cephalopod species (Nototodarus sloanii, Onykia ingens, and Octopus campbelli) (998, 1221 and 294 beaks, respectively, from 36 samples). All cephalopod specimens were juveniles, with N. sloanii (mean mantle length (ML) = 128.9 mm; mean mass (M) = 63.7 g) individuals being larger than O. ingens (mean ML = 73.9 mm; mean M = 23.6 g) and O. campbelli (mean ML = 0.4 mm; mean M = 0.6 g). By frequency of occurrence and mass, N. sloanii was the most important species (F% = 97.2; M% = 72.5) and O. ingens was the most important species by number (N% = 48.6). Mattern et al. (2009) found a higher diversity of cephalopods in the diet of Snares penguins in samples collected in Oct.-Nov. 2002 (N = 11 taxa versus 3 species in our study). The most important cephalopod species were the same in both studies (Nototodarus sloanii and Onykia ingens). Also, Mattern et al. (2009) found Histioteuthis atlantica, which is a squid associated with warm waters, and the pelagic octopod Ocythoe tuberculata, both still numerically relevant. These results suggest that Snares penguins may forage more in pelagic waters in the 2000’s than in 1980’s. According to stable isotope analysis, our study revealed that squid species, N. sloanii and O. ingens, occupied similar habitats (mean δ13C ± SD; -17.8 ± 0.2, -17.4 ± 0.5, respectively) on the continental shelf of Snares Islands, whereas the octopod species O. campbelli occupied a southern habitat (-18.5 ± 0.3). Moreover, O. campbelli feed on significantly higher trophic level prey (mean δ15N ± SD; 6.7 ± 0.5) when compared to N. sloanii and O. ingens (4.8 ± 0.9, 4.3 ± 0.9, respectively). O. campbelli is a benthic octopod and, in a benthic system, recycling of nutrients is typically enhanced, which usually translates into elevated δ15N values at the base of the trophic chain.The cephalopod species O. ingens and O. campbelli occurred both in the diet of Snares penguins and Eastern Rockhopper penguins (Eudyptes chrysocome filholi) (Campbell Islands). The δ13C values of O. ingens decrease from -17.6 ± 0.5 (Snares Islands) to -18.8 ± 0.8 (Campbell Islands, more south), suggesting that these individuals were not from the same population. Comparing δ13C values of O. campbelli (-18.5 ± 0.3) in Snares Island with the values from Campbell Island (-18.8 ± 0.6), the individuals were probably from the same population, as Snares penguins may have foraged more south to Sub-Antarctic waters, near at Campbell Island. Regarding the trophic level (δ15N) of O. ingens, this squid consumed by Snares penguins (4.3 ± 0.9) was of similar trophic level as O. ingens consumed by Eastern Rockhopper penguins (4.4 ± 0.6), suggesting that both individuals had similar diets. The trophic level of O. campbelli consumed by Snares penguins had bigger values (6.7 ± 0.5) compared to Eastern Rockhopper penguins (4.4 ± 0.8), inferring that perhaps O. campbelli had different diets.From a conservation perspective, in relation to local cephalopod fisheries, N. sloanii was already a target species in the 1980´s at the Snares Continental Shelf, catching bigger size squid (ML: 150-386 mm) than those found in the diet of Snares penguins, despite the high overlap between fishing and foraging areas. As in the 1980’s, nowadays local fisheries occur during Snares penguins breeding season, but as they breed only at Snares Islands (200 km south of the mainland), the risks of this species to interact with fisheries is lower when compared to other species, but can’t be overlooked. Climate change, which may affect the future availability of penguin prey, including cephalopods, might be a real threat in a short-term future.