A new environmental DNA pilot study by the New Zealand Penguin Initiative (NZPI) to find out what little penguins / kororā are eating focussed on two sites, the Otago Peninsula and the West Coast Penguin Trust’s study site at Camerons, Greymouth.
A summary of the NZPI pilot follows from Hiltrun Ratz:
What are kororā eating? eDNA Pilot Summary
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Adult Triplefin. Photo credit: The Fishes of New Zealand 2015 eds. Roberts, Stewart and Struthers.
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It’s been super exciting to get the go ahead to do a nationwide study on kororā diet this year. It’s just the start but we have results for two areas so far: Otago Peninsula and South Island West Coast. Scat – aka pooh – was collected in October and sent to Wilderlab for analyses of the DNA. These are then compared with known fish, crustaceans, molluscs etc. DNA and a list of species was sent back for the exciting bit of working out what the kororā have been eating.
While the results were not unexpected, they were surprising!
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Image Credit: Triplefin youngster. Palacios-Fuentes et al. 2014.
Kororā in Otago were eating mostly Triplefin (or cockabullies) and sprat – together almost 95%. Previous diet studies were based on hard parts of fish that identified the species and size, and Triplefin has never been recorded. So, what’s going on? Adult Triplefin grow to a length of 5-10cm (ideal for Kororā to eat) but they occur on the bottom of the ocean that is out of diving reach for Kororā – but the DNA was in the scat. Therefore, they must have been eating pelagic (or mid-water) youngsters. A bit more straight forward with sprat: they grow to 12cm long and occur in schools in coastal waters. Previous diet studies recorded >50% of sprat in the diet, a much higher percentage than recorded here.
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Image Credit: Blackhead Lanternfish; The Fishes of New Zealand 2015 eds. Roberts, Stewart and Struthers.
Kororā on the West Coast of South Island also brought a surprise: Almost two third of prey DNA was Blackhead Lanternfish, the next most important prey was Anchovy and Sprat. That makes sense because they all swim around mid-water and Kororā can reach them.
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There were other species present in both samples, but they were not important: Tarakihi, Squid, Hoki, Lightfish, Stargazers, Warehou, various species of Kopupu (Whitebait), Octopus, Greenbone, Gurnard and Thornfish. These species were likely taken as pelagic youngsters. There are four more samples being processed from the North Island and we are looking forward to finding out how the diet there is different to the pilot study from the South Island colonies. And then we are doing it all again in a couple of months to find out what kororā are eating during summer – and then autumn and winter.
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The main prey of our West Coast kororā were blackhead lanternfish or Lampichthys procerus, one of 250 species of lanternfish and one that seems to have avoided cameras – just a line drawing exists online. Apparently, they are found around the globe in the southern hemisphere in the region of the Subtropical Convergence. They grow up to 10cm long – perfect size for capture and swallow by kororā.
We will be collecting scat seasonally to contribute to this interesting and valuable study.
