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Cephalopod component of Snares Penguin (Eudyptes robustus) at Snares Islands, New Zealand in the 1980´s: relationships with local fisheries and implications on the penguin’s conservation

Hugo Guímaro1*, David Thompson2, Vitor H. Paiva1, Duncan Cunningham3, Philip Moors3 and José C. Xavier1, 4
  • 1 Department of Life Sciences, Faculty of Sciences and Technology, University of Coimbra, Portugal
  • 2 National Institute of Water and Atmospheric Research (NIWA), New Zealand
  • 3 Department of Conservation, New Zealand
  • 4 British Antarctic Survey (BAS), United Kingdom

In the Southern Ocean, 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 (48°1’32’’S, 166°36’54’’E), was used as a biological sampler to evaluate the cephalopod component of the diet of penguins around the Snares Islands during the 1980´s and to assess the habitat and trophic level of cephalopods (through stable isotope analyses of beak material). Snares penguin is classified as “vulnerable” according to the IUCN due to is restricted habitat and it is susceptible to anthropogenic activities. As historical diet data is rare for this species, we carried out detailed analyses of the diet of Snares penguins in the breeding season 1986-1987 (Nov.-Feb.). The results obtained show that they feed on three cephalopod species (Nototodarus sloanii, Onykia ingens, and Octopus campbelli) (998, 1221 and 294 beaks, respectively, from 36 samples). All specimens were juveniles, but 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 analyses, our study showed that all three species, N. sloanii, O. ingens, and O. campbelli occupied similar habitats (mean δ13C ± SD; -17.8 ± 0.2, -17.4 ± 0.5, -18.5 ± 0.3, respectively) on the continental shelf of Snares Islands. Moreover, O. campbelli prey 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 species 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, but more studies on its diet are required to understand this. In relation to local cephalopod fisheries, N. sloanii was already targeted commercially, in the 1980´s at the Snares Shelf, catching bigger size squids (ML: 150-386mm) (Uozumi, 1998) than those found in the diet of Snares penguins, despite both overlapping in their fishing/foraging areas. In the 1980’s and at these days, 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 these species to interact with fisheries is lower when compared to other species, but can’t be overlooked (Crawford et al. 2017). Climate change, which may affect the future availability of their prey, including cephalopods, might be a real threat in the near future (Trathan et al. 2014).

References

Mattern, T., D. M. Houston, C. Lalas, A. N. Setiawan and L. S. Davis (2009). "Diet composition, continuity in prey availability and marine habitat – keystones to population stability in the Snares Penguin (Eudyptes robustus)." Emu 109: 204-213. Uozumi, Y. (1998). "Fishery Biology of Arrow Squids, Nototodarus gouldi and N. sloanii, in New Zealand Waters." Bulletin of the National Research Institute of Far Seas Fisheries 35(1): 111. Crawford, R., U. Ellenberg, E. Frere, C. Hagen, K. Baird, P. Brewin, S. Crofts, J. Glass, T. Mattern, J. Pompert, K. Ross, J. Kemper, K. Ludynia, R. B. Sherley, A. Steinfurth, C. G. Suazo, P. Yorio, L. Tamini, J. C. Mangel, L. Bugoni, G. Jiménez Uzcátegui, A. Simeone, G. Luna-Jorquera, P. Gandini, E. J. Woehler, K. Pütz, P. Dann, A. Chiaradia and C. Small (2017). "Tangled and drowned: a global review of penguin bycatch in fisheries." Endangered Species Research 34: 373-396. Trathan, P. N., P. Garcia-Borboroglu, D. Boersma, C. A. Bost, R. J. Crawford, G. T. Crossin, R. J. Cuthbert, P. Dann, L. S. Davis, S. De La Puente, U. Ellenberg, H. J. Lynch, T. Mattern, K. Putz, P. J. Seddon, W. Trivelpiece and B. Wienecke (2014). "Pollution, habitat loss, fishing, and climate change as critical threats to penguins." Conservation Biology 29(1): 31-41.

Keywords: Snares Penguin, Diet, Nototodarus sloanii, Onykia ingens, Octopus campbelli

Conference: XX Iberian Symposium on Marine Biology Studies (SIEBM XX) , Braga, Portugal, 9 Sep - 12 Sep, 2019.

Presentation Type: Poster Presentation

Topic: Ecology, Biodiversity and Vulnerable Ecosystems

Citation: Guímaro H, Thompson D, Paiva VH, Cunningham D, Moors P and Xavier JC (2019). Cephalopod component of Snares Penguin (Eudyptes robustus) at Snares Islands, New Zealand in the 1980´s: relationships with local fisheries and implications on the penguin’s conservation. Front. Mar. Sci. Conference Abstract: XX Iberian Symposium on Marine Biology Studies (SIEBM XX) . doi: 10.3389/conf.fmars.2019.08.00071

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Received: 08 Jun 2019; Published Online: 27 Sep 2019.

* Correspondence: Mr. Hugo Guímaro, Department of Life Sciences, Faculty of Sciences and Technology, University of Coimbra, Coimbra, Coimbra, Portugal, h.r.r.g@hotmail.com