Population trends of African penguins Spheniscus demersus in the Western Cape, South Africa, and their breeding success have been linked to the abundance of their main prey, sardine Sardinops sagax and anchovy Engraulis encrasicolus. During the late 1990s and early 2000s, both fish species increased markedly in abundance, but after 2004, sardine biomass decreased to below average levels. In addition, adults of both stocks were principally located to the east of Cape Agulhas from 2001 to 2009 and were thus distant from seabird colonies on South Africa's West Coast. The number of African penguin pairs counted at Robben Island from 2001 to 2009 and the fledging period of chicks from successful nests increased and decreased in apparent response to the biomass of sardine prior to each breeding season, possibly linked through adult condition at the onset of breeding. Breeding success and chick-fledging rates increased during the study period and showed positive relationships with local food availability, indexed through the annual industrial catch of anchovy made within 56 km (30 nautical miles) of the colony. In addition, chick-fledging rates were depressed in 2-chick broods during years when anchovy contributed < 75% by mass to the diet of breeding birds. Previously reported relationships between the overall abundance of forage fish in South Africa and penguin breeding success were not supported. Taken together, these results highlight the combined importance of ensuring adequate local food availability for seabirds during the reproductive cycle and safeguarding regional prey abundance during the non-breeding season.

Global forage-fish landings are increasing, with potentially grave consequences for marine ecosystems. Predators of forage fish may be influenced by this harvest, but the nature of these effects is contentious. Experimental fishery manipulations offer the best solution to quantify population-level impacts, but are rare. We used Bayesian inference to examine changes in chick survival, body condition and population growth rate of endangered African penguins Spheniscus demersus in response to 8 years of alternating time–area closures around two pairs of colonies. Our results demonstrate that fishing closures improved chick survival and condition, after controlling for changing prey availability. However, this effect was inconsistent across sites and years, highlighting the difficultly of assessing management interventions in marine ecosystems. Nevertheless, modelled increases in population growth rates exceeded 1% at one colony; i.e. the threshold considered biologically meaningful by fisheries management in South Africa. Fishing closures evidently can improve the population trend of a forage-fish-dependent predator—we therefore recommend they continue in South Africa and support their application elsewhere. However, detecting demographic gains for mobile marine predators from small no-take zones requires experimental time frames and scales that will often exceed those desired by decision makers.

Reliable estimates of survival and dispersal are crucial to understanding population dynamics, but for seabirds, in which some individuals spend years away from land, mortality and emigration are often confounded. Multistate mark–recapture methods reduce bias by incorporating movement into the process of estimating survival. We used a multistate model to provide unbiased age‐specific survival and movement probabilities for the Endangered African Penguin Spheniscus demersus based on 5281 nestlings and 31 049 adults flipper‐banded and resighted in the Western Cape, South Africa, between 1994 and 2012. Adult survival was initially high (≥ 0.74) but declined after 2003–2004 coincident with a reduction in the availability of Sardine Sardinops sagax and Anchovy Engraulis encrasicolus on the west coast of South Africa. Juvenile survival was poorly estimated, but was lower and more variable than adult survival. Fidelity to the locality of origin varied over time, but was high in adults at Robben and Dassen islands (≥ 0.88) and above 0.55 for juvenile and immature Penguins at all localities. Movement occurred predominantly during 1994–2003 and was indicative of immigration to Robben and Dassen islands. Our results confirm that a prolonged period of adult mortality contributed to the observed decline in the African Penguin population and suggest a need for approaches operating over large spatial scales to ensure food security for marine top predators.

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Marine systems are under pressure from both climate change and exploitation. While many of these ecosystems are inherently variable and hard to monitor, seabirds can be used as ecological indicators that provide early warning signals of deeper environmental change. The Agulhas-Benguela marine ecosystem around southern Africa has exhibited long-term changes in sea surface temperature, and the distribution of pelagic fish in this system has shifted. The Cape gannet Morus capensis is a seabird endemic as a breeding species to the Agulhas-Benguela ecosystem. Cape gannets breed at just 6 locations and are listed by the IUCN as Vulnerable. Knowledge of the survival and movements of a species is important for understanding of factors influencing its conservation. A random effects multistate capture−recapture model was used to estimate the annual survival probabilities and movement between colonies for adult birds at the 3 South African colonies of the species. The effects on survival of environmental and fisheries-related covariates were explored. Survival over the 20 yr period did not exhibit any long-term trend at the 2 southern colonies (Malgas and Bird Islands) but decreased at Lambert's Bay between 1996 and 2007. At all 3 colonies, adult birds showed a high degree of site fidelity. It may be that for Cape gannets, the primary effects of climate and fishing are on recruitment rather than on survival. The continued use of sub-optimal conditions by the west coast colonies has been referred to as an 'ecological trap' and necessitates the introduction of spatial considerations into fisheries management. KEY WORDS: Cape gannets · Multistate capture−recapture models · Fisheries management · Ecological indicator · Seabirds · Survival Resale or republication not permitted without written consent of the publisherMar Ecol Prog Ser 461: [245][246][247][248][249][250][251][252][253][254][255] 2012 The Benguela upwelling ecosystem off south-western Africa is 1 of 4 major eastern boundary currents in the world's oceans and is a highly productive ecosystem which supports both sardine Sardinops sagax and anchovy Engraulis encrasicolus as the main forage fish species for several predators (Crawford 2007, Gremillet et al. 2008a). The Agulhas Current flows from the Mozambique Channel around the eastern and southern part of South Africa (Fig. 1). Both the Agulhas Current ecosystem and the southern Benguela ecosystem have exhibited long-term changes in sea surface temperature, with a cooling in the southern Benguela and a warming of the Agulhas Current over the past 2 decades (Roy et al. 2007, Rouault et al. 2009.Seabirds and other predators at the top of the food chain are especially vulnerable to ecosystem perturbations and are often used as indicators for the state of oceanic ecosystems (Piatt et al. 2007, Durant et al. 2009, Rolland et al. 2010. In particular, predators that forage on a small number of key fish species should be better indicators for the state of the system than more generalist predators that can adapt...