Local purse-seine fishers' economic losses owing to endangered seabird conservation measures – perceptions and reality

The likelihood of success of a marine protected area (MPA) is strongly dependent on stakeholders’ support. A concern often raised by local fishers is their lack of involvement in the design or management of a MPA and their loss of income owing to lost fishing grounds. We used Algoa Bay, South Africa, as a case study to analyse fisher’s and fish-processing factory managers’ concerns and perceived economic losses from fishing closures using structured interviews. Since 2009, a 20 km-radius purse-seine fishing-exclusion zone has been tested in Algoa Bay to assess the benefit to population recovery of the endangered African penguin Spheniscus demersus. Costs to the industry were estimated in terms of loss of catches and additional travel time to fishing grounds with and without closures. Fisher responses to interviews revealed general support for conservation and MPAs, but individuals interviewed did not feel that the 20 km fishing exclusion zones in Algoa Bay would aid African penguin conservation. While they systematically raised concerns about potential economic costs to their industry from closures, neither their catch sizes nor travel times varied significantly with fishing exclusion measures. Acknowledgement and assessment of the economic concerns may aid in initiating an informed dialogue amongst the various stakeholders in Algoa Bay, which may increase compliance and success of the newly proclaimed Addo elephant National Park MPA. Continued dialogue may also act as a catalyst for more integrated ocean management of biodiversity and human uses in the bay

Urofaecal glucocorticoid metabolite concentrations in African penguin (Spheniscus demersus) chick populations experiencing different levels of human disturbance

Despite the importance of ecotourism in species conservation, little is known about the industry’s effects on wildlife. In South Africa, some African penguin (Spheniscus demersus) colonies have become tourist attractions. The species is globally endangered, with population sizes decreasing over the past 40 years. As African penguin chicks are altricial and unable to move away from anthropogenic stressors, it is important to evaluate the effect of tourist activities on baseline glucocorticoid levels as a measure of potential disturbance. Chicks at three study sites within two breeding colonies (Robben Island, Stony Point), with varying levels of exposure to tourism (low/moderate/high) were monitored. Urofaecal samples were collected to determine urofaecal glucocorticoid metabolite (ufGCM) concentrations as an indication of baseline stress physiology. Morphometric measurements were taken to compare body condition between sites. Penguin chicks experiencing low, infrequent human presence had significantly higher mean (± standard deviation) ufGCM levels [1.34 ± 1.70 μg/g dry weight (DW)] compared to chicks experiencing both medium (0.50 ± 0.40 μg/g DW, P = 0.001) and high levels of human presence (0.57 ± 0.47 μg/g DW, P = 0.003). There was no difference in chick body condition across sites. These results suggest that exposure to frequent human activity may induce habituation/desensitization in African penguin chicks. Acute, infrequent human presence was likely an important driver for comparatively higher ufGCM levels in chicks, though several other environmental stressors may also play an important role in driving adrenocortical activity. Nevertheless, as unhabituated chicks experiencing infrequent anthropogenic presence showed significantly higher ufGCM levels, managers and legislation should attempt to minimize all forms of activity around important breeding colonies that are not already exposed to regular tourism. Although the results of this study are crucial for developing enhanced conservation and management protocols, additional research on the long-term effect of anthropogenic activities on African penguin physiology is required.Department of Biodiversity and Conservation Biology, African National Research Foundation and Earthwatch Institute.http://conphys.oxfordjournals.orgdm2022Mammal Research InstituteZoology and Entomolog

Recreational fish-finders - an inexpensive alternative to scientific echo-sounders for unravelling the links between marine top predators and their prey

Studies investigating how mobile marine predators respond to their prey are limited due to the challenging nature of the environment. While marine top predators are increasingly easy to study thanks to developments in bio-logging technology, typically there is scant information on the distribution and abundance of their prey, largely due to the specialised nature of acquiring this information. We explore the potential of using single-beam recreational fish-finders (RFF) to quantify relative forage fish abundance and draw inferences of the prey distribution at a fine spatial scale. We compared fish school characteristics as inferred from the RFF with that of a calibrated scientific split-beam echo-sounder (SES) by simultaneously operating both systems from the same vessel in Algoa Bay, South Africa. Customized open-source software was developed to extract fish school information from the echo returns of the RFF. For schools insonified by both systems, there was close correspondence between estimates of mean school depth (R 2 = 0.98) and school area (R 2 = 0.70). Estimates of relative school density (mean volume backscattering strength; S v ) measured by the RFF were negatively biased through saturation of this system given its smaller dynamic range. A correction factor applied to the RFF-derived density estimates improved the comparability between the two systems. Relative abundance estimates using all schools from both systems were congruent at scales from 0.5 km to 18 km with a strong positive linear trend in model fit estimates with increasing scale. Although absolute estimates of fish abundance cannot be derived from these systems, they are effective at describing prey school characteristics and have good potential for mapping forage fish distribution and relative abundance. Using such relatively inexpensive systems could greatly enhance our understanding of predator-prey interactions

Bayesian inference reveals positive but subtle effects of experimental fishery closures on marine predator demographics

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

Key Challenges in Advancing an Ecosystem-Based Approach to Marine Spatial Planning Under Economic Growth Imperatives

In 2017, South Africa became the first African country to draft Marine Spatial Planning (MSP) legislation. The underlying legal framework supports the achievement of ecological, social and economic objectives, but a national policy to fast track the oceans economy provides a challenge for ecosystem-based approaches to MSP. During the 2018 International Marine Conservation Congress, we convened a session to present particular challenges that will likely apply to any developing country seeking to increase profits from existing, or proposed, marine activities. Here we present six multi-disciplinary research projects that support ecosystem-based approaches to MSP in South Africa, by addressing the following knowledge gaps and specific key challenges: (1) the lack of data-derived measurements of ecosystem condition (and the need to validate commonly-used proxy measures); (2) the need to develop models to better understand the potential impacts of climate change on food webs and fisheries; (3) the slow implementation of an ecosystem approach to fisheries management, and the need to implement existing legal instruments that can support such an approach; (4) the paucity of evidence supporting dynamic ocean management strategies; (5) the requirement to manage conflicting objectives in growing marine tourism industries; and (6) the need to adopt systems thinking approaches to support integrated ocean management. We provide examples of specific research projects designed to address these challenges. The ultimate goal of this research is to advance a more integrated approach to ocean management in South Africa, using tools that can be applied in countries with similar socio-political and environmental contexts

Stratégies de recherche alimentaire d’oiseaux marins vulnérables dans le Benguela.

Dans un contexte de changements globaux rapides, il est crucial de comprendre les mécanismes de recherche alimentaire des prédateurs marins supérieurs afin de déterminer leur capacité d’adaptation face à la variabilité environnementale, dans le but de prédire les conséquences de ces changements sur la dynamique de leurs populations et de définir des mesures de conservation appropriées pour ces espèces menacées et les réseaux trophiques auxquels elles participent. Dans l’upwelling du Benguela, en Afrique du Sud, les fous du Cap (Morus capensis) et les manchots du Cap (Spheniscus demersus) sont vulnérables d’extinction et font face depuis une dizaine d’années au déplacement vers le sud-est de leurs proies principales, les sardines (Sardinops Sagax) et les anchois (Engraulis encrasicolus), sous l’influence probable des changements climatiques. Nous avons effectué une étude détaillée des stratégies de recherche alimentaire des fous du Cap au moyen d’enregistreurs électroniques miniaturisés portés par ces oiseaux tout au long de leurs voyages en mer, ainsi que des suivis de leur régime alimentaire et de l’abondance et de la distribution de leurs proies dans le Benguela. Nous avons montré que les fous du Cap sont capables d’augmenter substantiellement leur effort de prospection alimentaire face à une faible disponibilité des proies naturelles sur la côte ouest de l’Afrique du Sud. Ils restent pourtant limités dans l’étendue de leur aire de recherche alimentaire par la nécessité de retourner régulièrement à la colonie pour nourrir leur progéniture. Ils se tournent alors vers des proies de substitution, des déchets de pêche au merlu (Merluccius spp.) de faible valeur nutritive. Ces proies représentent de la « Junk-food » pour les poussins de fous et ont un impact négatif sur leur survie. Même s’ils permettent aux adultes de réduire significativement leur effort de prospection en hiver, les déchets de pêche ne compensent donc pas la faible disponibilité des sardines et des anchois au cours de la saison de reproduction. Nous avons déterminé que pour une densité des proies naturelles inférieure à 25 g m-2 dans l’aire de nourrissage des fous du Cap, les adultes reproducteurs ne parviennent plus à équilibrer leur balance énergétique et échouent massivement au cours de la reproduction. Poussés par la fidélité à leur site de reproduction, les fous du Cap étudiés reviennent cependant tenter de se reproduire dans des conditions environnementales sub-optimales et se retrouvent victimes d’un piège écologique. La structure sociale d’une espèce peut donc ralentir son adaptation aux changements environnementaux. Les petits poissons pélagiques, sardines et anchois, sont désormais rares au large de la côte ouest de l’Afrique du Sud et la compétition des oiseaux marins du Benguela avec les pêcheries industrielles à la senne atteint son paroxysme. La biotélémétrie, particulièrement le suivi GPS des fous et des manchots du Cap en mer, nous a permis de définir leurs zones d’alimentation de manière très précise. En nous basant sur ces données et sur des suivis des activités de pêche à la senne, nous proposons des mesures de conservation qui prennent en compte les zones d’alimentation des prédateurs supérieurs concernés tout en considérant les besoins économiques locaux. Ces zones permettront le maintien des populations d’oiseaux marins menacées et nos données alimenteront également les plans de gestion écosystémique des pêcheries dans le but d’une exploitation durable des ressources naturelles.In the context of rapid global changes, understanding the foraging mechanisms of marine top predators is crucial to determine their ability to adapt to environmental variability, in order to predict the consequences of changes on population dynamics and to define appropriate conservation measures for threatened species and the trophic webs to which they belong. In the Benguela upwelling system, in South Africa, Cape gannets (Morus capensis) and African penguins (Spheniscus demersus) are vulnerable to extinction and are facing for 10 years onward a progressive south-eastward shift of their main prey, sardines (Sardinops Sagax) and anchovies (Engraulis encrasicolus), probably due to climate change. We performed a detailed study on Cape gannet foraging strategies, using birdborne recorders, and analysing their diet and the distribution and abundance of their prey in the Benguela. We showed that Cape gannets are able to increase substantially their foraging effort facing poor natural prey availability on the west coast of South Africa. However they are limited in the extent of their foraging area by the need to regularly come back to the colony to feed their young. Thus they turn to feeding behind trawlers on hake fishery discards (Merluccius spp.) of poor nutritional content. These prey represent « Junk-food » for the gannet chicks and have a negative impact on their survival. Even if they allow adults to significantly decrease their foraging effort during winter, fishery discards can not compensate for a poor availability in sardines and anchovies during the breeding season. We have determined that below a density of 25 g m-2 of natural prey in their foraging area, breeding Cape gannets can not equilibrate their energy balance and fail massively in their breeding attempt. Faithful to their breeding site, Cape gannets come back to attempt breeding under sub-optimal conditions, and so are lead to an ecological trap, instead of emigrating. The social structure of a species can therefore lag its adaptation to environmental changes. Small pelagic fish, sardines and anchovies, are currently scarce off the west coast of South Africa, enhancing the competition between seabirds and purse-seine fisheries. Biotelemetry, and particularly GPS tracking on Cape gannets and African penguins at sea, allowed us to precisely define theses birds’ foraging zones. Basing our decision on these data and on purse-seine fisheries activities, we suggest conservation measures that take into account foraging areas of these top predators, while considering local economic needs. These zones are crucial for the maintenance of threatened endemic populations and our data would help in an ecosystemic approach to fisheries management, for a sustainable exploitation of the environment

Foraging strategies of vulnerable seabirds in the Benguela

Dans un contexte de changements globaux rapides, il est crucial de comprendre les mécanismes de recherche alimentaire des prédateurs marins supérieurs afin de déterminer leur capacité d'adaptation face à la variabilité environnementale, dans le but de prédire les conséquences de ces changements sur la dynamique de leurs populations et de définir des mesures de conservation appropriées pour ces espèces menacées et les réseaux trophiques auxquels elles participent. Dans l'upwelling du Benguela, en Afrique du Sud, les fous du Cap (Morus capensis) et les manchots du Cap (Spheniscus demersus) sont vulnérables d'extinction et font face depuis une dizaine d'années au déplacement vers le sud-est de leurs proies principales, les sardines (Sardinops Sagax) et les anchois (Engraulis encrasicolus), sous l'influence probable des changements climatiques. Nous avons effectué une étude détaillée des stratégies de recherche alimentaire des fous du Cap au moyen d'enregistreurs électroniques miniaturisés portés par ces oiseaux tout au long de leurs voyages en mer, ainsi que des suivis de leur régime alimentaire et de l'abondance et de la distribution de leurs proies dans le Benguela. Nous avons montré que les fous du Cap sont capables d'augmenter substantiellement leur effort de prospection alimentaire face à une faible disponibilité des proies naturelles sur la côte ouest de l'Afrique du Sud. Ils restent pourtant limités dans l'étendue de leur aire de recherche alimentaire par la nécessité de retourner régulièrement à la colonie pour nourrir leur progéniture. Ils se tournent alors vers des proies de substitution, des déchets de pêche au merlu (Merluccius spp.) de faible valeur nutritive. Ces proies représentent de la Junk-food pour les poussins de fous et ont un impact négatif sur leur survie. Même s'ils permettent aux adultes de réduire significativement leur effort de prospection en hiver, les déchets de pêche ne compensent donc pas la faible disponibilité des sardines et des anchois au cours de la saison de reproduction. Nous avons déterminé que pour une densité des proies naturelles inférieure à 25 g m-2 dans l'aire de nourrissage des fous du Cap, les adultes reproducteurs ne parviennent plus à équilibrer leur balance énergétique et échouent massivement au cours de la reproduction. Poussés par la fidélité à leur site de reproduction, les fous du Cap étudiés reviennent cependant tenter de se reproduire dans des conditions environnementales sub-optimales et se retrouvent victimes d'un piège écologique. La structure sociale d'une espèce peut donc ralentir son adaptation aux changements environnementaux. Les petits poissons pélagiques, sardines et anchois, sont désormais rares au large de la côte ouest de l'Afrique du Sud et la compétition des oiseaux marins du Benguela avec les pêcheries industrielles à la senne atteint son paroxysme. La biotélémétrie, particulièrement le suivi GPS des fous et des manchots du Cap en mer, nous a permis de définir leurs zones d'alimentation de manière très précise. En nous basant sur ces données et sur des suivis des activités de pêche à la senne, nous proposons des mesures de conservation qui prennent en compte les zones d'alimentation des prédateurs supérieurs concernés tout en considérant les besoins économiques locaux. Ces zones permettront le maintien des populations d'oiseaux marins menacées et nos données alimenteront également les plans de gestion écosystémique des pêcheries dans le but d'une exploitation durable des ressources naturellesIn the context of rapid global changes, understanding the foraging mechanisms of marine top predators is crucial to determine their ability to adapt to environmental variability, in order to predict the consequences of changes on population dynamics and to define appropriate conservation measures for threatened species and the trophic webs to which they belong. In the Benguela upwelling system, in South Africa, Cape gannets (Morus capensis) and African penguins (Spheniscus demersus) are vulnerable to extinction and are facing for 10 years onward a progressive south-eastward shift of their main prey, sardines (Sardinops Sagax) and anchovies (Engraulis encrasicolus), probably due to climate change. We performed a detailed study on Cape gannet foraging strategies, using birdborne recorders, and analysing their diet and the distribution and abundance of their prey in the Benguela. We showed that Cape gannets are able to increase substantially their foraging effort facing poor natural prey availability on the west coast of South Africa. However they are limited in the extent of their foraging area by the need to regularly come back to the colony to feed their young. Thus they turn to feeding behind trawlers on hake fishery discards (Merluccius spp.) of poor nutritional content. These prey represent Junk-food for the gannet chicks and have a negative impact on their survival. Even if they allow adults to significantly decrease their foraging effort during winter, fishery discards can not compensate for a poor availability in sardines and anchovies during the breeding season. We have determined that below a density of 25 g m-2 of natural prey in their foraging area, breeding Cape gannets can not equilibrate their energy balance and fail massively in their breeding attempt. Faithful to their breeding site, Cape gannets come back to attempt breeding under sub-optimal conditions, and so are lead to an ecological trap, instead of emigrating. The social structure of a species can therefore lag its adaptation to environmental changes. Small pelagic fish, sardines and anchovies, are currently scarce off the west coast of South Africa, enhancing the competition between seabirds and purse-seine fisheries. Biotelemetry, and particularly GPS tracking on Cape gannets and African penguins at sea, allowed us to precisely define theses birds foraging zones. Basing our decision on these data and on purse-seine fisheries activities, we suggest conservation measures that take into account foraging areas of these top predators, while considering local economic needs. These zones are crucial for the maintenance of threatened endemic populations and our data would help in an ecosystemic approach to fisheries management, for a sustainable exploitation of the environment