Laureline Meynier

Quantitative fatty acid signature analysis on New Zealand sea lions: model sensitivity and diet estimates

Abstract We used quantitative fatty acid signature analysis (QFASA) to predict the long-term diet of New Zealand (NZ) sea lions (Phocarctos hookeri) incidentally caught in the NZ arrow squid (Nototodarus spp.) fishery. The QFASA model used fatty acid (FA) profiles based on 82 blubber samples of NZ sea lions bycaught between 2000 and 2006. First, the model was optimized by a series of simulations for which 1 model parameter—6 different sets of calibration coefficients (CCs) from different pinniped species and feeding regime, 2 sets of FAs, and the consideration of individual prey values, or mean prey values—varied each time. The best-fit parameters were those giving the lowest Kullback–Liebler distance values. Second, these parameters were used in a model to estimate the diet of NZ sea lions. QFASA was highly sensitive to the set of CCs applied. Across years the most important prey estimated with the best-fit CCs were southern arrow squid (Nototodarus sloani, 18–28% mass), hoki (Macruronus novaezelandiae, 10–27% mass), rattails (Macrouridae, 7–27% mass), and possibly scampi (Metanephrops challengeri, 1–19% mass). Despite the uncertainty on the accuracy of the match between the best-fit CCs used and the true FA metabolism of NZ sea lions, the variation of prey estimated among years was highly consistent with the trends of commercial catches during the same period, providing some confidence in the present QFASA predictions. The most important estimated prey were demersal species living mainly at depths >200 m that NZ sea lions encounter on the slopes of the Auckland Islands shelf. Our study emphasized the importance of these areas for bycaught NZ sea lions over the 1st half of the lactation period.

Food and feeding ecology of the striped dolphin, Stenella coeruleoalba , in the oceanic waters of the north-east Atlantic

The food and feeding ecology of the striped dolphin, Stenella coeruleoalba , in the oceanic waters of the north-east Atlantic were studied using the stomach contents of 60 striped dolphins caught in the albacore drift-net fishery throughout the summer months of 1992 and 1993 off the Bay of Biscay. Thirty-eight per cent of these dolphins were calves (0–1 years old), 25% were juveniles (2–8) and 37% were mature adults (9–32, of which 7 females and 14 males). The diet was found to be primarily composed of fish (39% by mass (M)) and cephalopods (56% M) and secondarily of crustaceans (5% M). The most significant fish family identified was the lanternfish (24% M) with Notoscopelus kroeyeri and Lobianchia gemellarii being predominant. Among squid, the oceanic Teuthowenia megalops and Histioteuthis spp. were the most significant. The pelagic shrimp Sergastes arcticus and Pasiphaea multidentata were the most prevalent crustaceans. Prey sizes ranging from 30 to 170 mm accounted for 80% of the prey items while 80% of the reconstituted biomass consisted of prey measuring between 60 and 270 mm. Prey composition and size-range differed slightly with sex and age or body size of the dolphins. The state of digestion of food remains suggested that predation took place at dusk or during the early hours of the night on which the dolphins were caught.

Stomach contents of common dolphin (Deiphinus sp.) from New Zealand waters

Abstract This paper provides the first report of stomach contents of common dolphin (Deiphinus sp.) from New Zealand waters. We examined 53 stomachs from 42 stranded and 11 by‐caught common dolphin from the North Island of New Zealand between 1997 and 2006. Although the diet of by‐caught and stranded common dolphin comprised a diverse range of fish and cephalopod species, the prevalent prey were arrow squid Nototodarus spp., jack mackerel Trachurus spp., and anchovy Engraulis australis. Stranded dolphins that originated from coastal waters, and dolphins by‐caught within neritic waters, fed on both neritic and oceanic prey. Moreover, this mixed prey composition was evident in the diet of common dolphin by‐caught in oceanic waters, suggesting inshore/offshore movements of common dolphin on a diel basis.

Proximate composition, energy content, and fatty acid composition of marine species from Campbell Plateau, New Zealand

Abstract Campbell Plateau is an important fishing ground for the main commercial New Zealand species. Yet, studies on trophic interactions between species and their nutritional values are limited. The objectives of this study were to determine the proximate composition and energy contents of selected commercial and non‐commercial marine species from Campbell Plateau and their fatty acid (FA) composition, and to evaluate the degree to which species can be differentiated by their FA compositions. We analysed 43 fish specimens from 5 different species (Macruronus novaezelandiae, Lepidorhynchus denticulatus, Pseudophycis backus, Hemerocoetes spp. and Squalus acanthias), 17 cephalopod specimens from 2 species (Nototodarus sloani and Enteroctopus zealandicus), and 6 Metanephrops challengeri (crustacean). The variation of energy contents between fish species was not significant, but their lipid and protein contents varied significantly. FA signatures distinguished the species analysed and, at a broader scale, the type of habitat. Within‐specie s variability was important for benthic species. In general, the diet inference from FA trophic markers was consistent with reported diets from stomach contents.

Estimating size of opalfish from otoliths: implications for analyses of New Zealand sea lion diet

Anomalies can arise when species-specific otolith equations are applied to congeneric species in analyses of seal prey remains. Opalfishes, Hemerocoetes, two spp., are the most numerous fish in the diet of New Zealand sea lions, Phocarctos hookeri, at their population base at the Auckland Islands. Opalfish identified from otoliths in sea lion prey remains accounted for one-third of prey items in this and two previous diet studies. This highlighted the need to estimate size of opalfish accurately. Equations to estimate fish size from otolith length differed between the two species because otoliths of H. morelandi were relatively smaller than otoliths of H. artus. However, otoliths of these species were indistinguishable and this precluded definitive estimates of opalfish length and mass from otoliths. In particular, misidentification of otoliths could create untenably large estimates for fish size. A combination of the equations for otolith size to fish size from the two species avoided this anomaly and superseded previously published equations.

Tuberculosis in a New Zealand (Hooker's) sea lion

Abstract Extract Tuberculosis has been described in seven species of pinnipeds. Based on host preference, phenotype and genetic and antigenic testing, the causal bacterium has been classified as a distinct species, Mycobacterium pinnipedii, within the M. tuberculosis complex. An adult male New Zealand sea lion (Phocarctos hookeri) was found dead on the Otago coastline in mid 2005. Gross necropsy revealed multiple caseous foci throughout the lungs, subcutaneous and thoracic lymph nodes, and mesenteric lymph nodes. Histopathological examination showed granulomatous lesions containing numerous intra-lesional acid fast organisms. The organism was confirmed as being a member of the M. tuberculosis complex, based on restriction enzyme analysis. Spoligotyping is pending. This is the first confirmed case of mycobacterial disease in a New Zealand sea lion.