Cost-Effective fish survey tool detect African Penguin prey


Image by Claudio Velasques Rojas (Homebrew Films)

Fish surveys can potentially play an important role in the survival rate of the endangered African penguin.
A cost effective tool has been developed to detect their prey, say researchers. This can provide information to inform fishing management decisions affecting these endemic birds.The African penguin – the only penguin species breeding on the African continent – is classified as endangered because it is undergoing a very rapid population decline. The numbers of these endemic penguins (Spheniscus demersus) have decreased drastically over the last few decades, with a massive 70% decline of this iconic species in the past ten years. This trend currently shows no sign of reversing, and immediate conservation action is required to prevent further declines. The decrease in population is largely attributed to food shortage, assumed to be the result of large catches of fish, and environmental fluctuations. From previous studies carried out on the West Coast of South Africa, it seems there is a close association between the availability of the penguin’s prey –sardines and anchovy – and its survival as a species.

Often called the Jackass Penguin, these birds feed mostly in the open sea on pelagic, shoaling (swimming in groups) fish such as pilchards and anchovies as well as small squid. Moulting occurs annually and birds remain on land and do not feed during this period. They are found in marine and coastal habitats, predominantly on the offshore islands of the cold, nutrient-rich Benguela system.

In 2008, a multi-party island closure task team was set up by the Department of Agriculture, Forestry and Fisheries to conduct research on African penguins and assess the potential impact of purse-seine fishing on penguins during their breeding season. Comprising government, fisheries representatives and scientists, the task team initiated the implementation of experimental fishing exclusion zones within a 20 km radius of four islands on the west and south coasts of SA – which alternated between open and closed in different years, between 2008 and 2014. The findings of this experiment are currently being assessed in order to formulate recommendations to government with regards to the potential influence of commercial fishing on the conservation status of this species.

The Responsible Fisheries Alliance (RFA) has also been funding research on these birds to gain a better understanding of the situation as well as insight into potential management options.
Dr Lorien Pichegru and Alistair McInnes of the University of Cape Town’s Percy FitzPatrick Institute of African Ornithology were supported by the Alliance in their study to assess the impact of fishing on prey abundance and penguin populations on the south coast.

Since 2008, intense monitoring of penguins on two islands in Algoa Bay off the coast of Port Elizabeth included GPS tracking of chick-rearing penguins as well as monitoring chick growth rates, breeding success and diet. St Croix Island is host to the world’s largest colony of African penguins and was closed to purse-seine fishing from 1 January 2009 to 31 December 2011. Nearby Bird Island remained open to fishing until 1 January 2012 and it was then declared closed to fishing for three years.

According to Dr Pichegru, it is evident that penguin foraging efforts increased with the size of commercial catches in the vicinity of the colony, and decreased with the fishing exclusion.  In other words, their research shows that these birds have to look for food further from home than before. However, limiting fishing over a small area around an island does not automatically ensure good fish availability for penguins as prey populations are subject to natural fluctuations such as changing oceanographic conditions.

The researchers also explored links between penguin foraging ecology and fish availability, both with and without the influence of commercial fishing pressure. In 2013, with additional financial support from the RFA, Pichegru and McInnes conducted fish surveys during the same time as they were monitoring penguins on the islands. They investigated the impact of fishing pressure on the availability of penguin prey as well as the relationship between food availability and foraging behaviour.

Dr Pichegru explains, “The study revealed that, while the size of the commercial catches clearly influences penguins’ foraging effort, the magnitude of such influence certainly depends on local fish abundance, which can vary annually. From these surveys, foraging effort of breeding African penguins can be related to fish abundance in Algoa Bay.”

Says Dr Pichegru, “The small pelagic fish surveys that were conducted in this study are extremely cost effective and could potentially be a powerful tool to facilitate adaptive management strategies of fisheries over small temporal and spatial scales.” She suggests that local abundance of small pelagic fish and variation in such abundance could be assessed rapidly on a monthly basis, and fishing behaviour adjusted accordingly. “While the feasibility and the design of such management strategies should be further explored, they would certainly benefit African penguins, while limiting socio-economic impacts on the fishing industry.”

All breeding sites along the South African coast are either protected in South African National Parks or provincial or local authority nature reserves, or by other relevant authorities. The African Penguin is listed under the Threatened of Protected Species Regulations of the National Biodiversity Act, elevating its protection status to a national level.

Attachments

  1. Foraging strategies and habitat utilisation of the African penguin around Robben and Dassen Islands (204.4 KiB)
    Foraging strategies and habitat utilisation of the African penguin around Robben and Dassen Islands

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