Amber-Robyn Childs

Amber-Robyn Childs
Rhodes University | RU · Department of Ichthyology and Fisheries Science

PhD

About

57
Publications
10,031
Reads
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733
Citations
Citations since 2016
37 Research Items
503 Citations
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2016201720182019202020212022020406080100120
2016201720182019202020212022020406080100120
2016201720182019202020212022020406080100120
Introduction
My research is centred on the biology, ecology, physiology and movement behaviour (acoustic telemetry) of estuarine and coastal fishes, with implications for fisheries and climate change.
Additional affiliations
January 2019 - April 2019
Rhodes University
Position
  • Professor (Associate)
January 2014 - present
Rhodes University
Position
  • Lecturer

Publications

Publications (57)
Article
Fishers’ ecological knowledge (FEK) has become a popular method for collecting fisheries data. Yet, standard biological sampling by researchers is still the most commonly used method. South Africa’s recreational fishing sector currently has a wealth of biological and demographic information on species captured with hook and line, while several spec...
Article
Recreational fisheries are notoriously hard to manage, monitor and govern. This often requires managers to think “out of the box” and disregard traditional methodologies designed to manage fisher behaviour. Social media, which is an informal technological scholastic platform for the communication and dissemination of information, has become an impo...
Article
Argyrosomus japonicus is arguably South Africa’s most important estuarine recreational and small-scale fishery species. Although juvenile A. japonicus predominate in estuarine environments, where catch-and-release angling is common, limited C&R studies have taken place. The aim of this study was to use angler-behaviour to robustly examine the physi...
Article
Full-text available
Estuaries serve as important nursery habitats for several coastal fishery species. The successful recruitment of larvae and early juveniles into estuaries is paramount for population persistence and maintenance. Several factors have been proposed as stimuli that could elicit a recruitment response in estuary-associated fish species. Larvae and earl...
Article
Fishing guides are held in high esteem by recreational fishing clients whom they likely influence (for better or worse) through role-modelling. This, coupled with consensus that angler behaviour is a key determinant of ecological outcomes in the catch-and-release (C&R) process suggests exploring the state of fishing guide knowledge, attitudes and b...
Article
Full-text available
The South African spearfishery targets a variety of data-deficient species, which are consequently poorly managed. This study aimed to describe the age and growth of one of these species, the Cape knifejaw, Oplegnathus conwayi, which is endemic to the southern and eastern coasts of South Africa. Monthly biological samples were collected through res...
Article
Knowledge of the location and timing of spawning events is critical for fisheries management. As is the case for many southern African fishes, the spotted grunter Pomadasys commersonnii was historically thought to reproduce in the coastal waters off KwaZulu-Natal Province (KZN), South Africa, with subsequent egg and larval dispersal towards the Eas...
Article
Full-text available
Changes in behaviour and physiology are the primary responses of fishes to anthropogenic impacts such as climate change and over-fishing. Behavioural changes (such as a shift in distribution or changes in phenology) can ensure that a species remains in an environment suited for its optimal physiological performance. However, if fishes are unable to...
Article
Recent investigations suggest that global warming is likely to alter temperature regimes along the southeastern coastline of South Africa through the increased frequency of upwelling events. Identifying thermal thresholds is fundamental in predicting the response of marine ectotherms to rapidly changing ocean temperatures. The aim of this study was...
Article
Sagittal otolith pairs were extracted from two-hundred-and-twenty-six giant African threadfin Polydactylus quadrifilis collected from the Kwanza Estuary in Angola between 2016 and 2018 ranging in size from 160 to 1360 mm fork-length (FL) and from one to 23 years of age (26 juvenile, 170 male, nine intersex and 27 female). An additional 85 otolith p...
Article
Full-text available
Ocean acidification is predicted to have widespread impacts on marine species. The early life stages of fishes, being particularly sensitive to environmental deviations, represent a critical bottleneck to recruitment. We investigated the effects of ocean acidification (∆pH = −0.4) on the oxygen consumption and morphometry during the early ontogeny...
Article
Linefish' is a uniquely South African term used to describe marine fishes that are captured using hook and line. The South African linefishery is a complex socio-ecological system that has a considerable impact on the coastal marine environment while generating social and economic benefits for commercial, small-scale and recreational fishers. Like...
Article
Best-practice guidelines to improve recreational fishers’ handling during catch-and-release (C&R) events are critical to improve the conservation and management of fish stocks worldwide. While best-practice research is growing, there are knowledge gaps, with the effects of sand exposure on fish mucous membranes understudied. This study aimed to det...
Article
Full-text available
Foreign fishing tourism (FFT) is becoming increasingly popular in the developing world, where it often coexists alongside other important sectors involving domestic recreational anglers and dependant artisanal and subsistence fishing communities. Therefore, it is important that FFT operations use effective catch‐and‐release (C&R) angling to minimis...
Article
Catch-and-release (C&R) angling has increased in popularity through its mandatory and voluntary use in fisheries conservation and management. However, research has shown that fish can experience considerable stress during a C&R event. The physiological response of fishes is typically assessed by measuring the concentrations of blood-plasma cortisol...
Article
Full-text available
It has been suggested that tourism fisheries can raise the value of landed catch, provide alternative livelihoods for local artisanal fishers and, because recreationally caught fishes are often released, simultaneously conserve stocks. However, for fishing tourism to meet ecotourism standards, sustainable, local economic benefit is imperative. This...
Article
Full-text available
Quantifying how the heart rate of ectothermic organisms responds to environmental conditions (e.g. water temperature) is important information to quantify their sensitivity to environmental change. Heart rate studies have typically been conducted in lab environments where fish are confined. However, commercially available implantable heart rate bio...
Book
Full-text available
The Southern African Marine Linefish Symposium is an event where scientists come together and present any contemporary research relating to linefisheries in the region. The symposium occurs every 4 - 7 years depending on circumstances and the research presented at each event is summarized and published in the form of a proceedings document. The lat...
Article
The population of Cape fur seal Arctocephalus pusillus pusillus at Ilha dos Tigres off the coast of southern Angola is expanding. Until now the only available biological information on the population has been its demographic parameters, and this insufficiency has hindered our understanding of the population’s ecology. The current study aimed to des...
Article
Although marine recreational fisheries are socially and economically important, there is often limited funding for their monitoring and assessment. With South African anglers reporting catch declines for almost all targeted species and little long-term monitoring data available, novel methods need to be explored to provide managers with additional...
Article
Life-cycle diversity is the existence of alternative strategies among coexisting individuals within the same population and is an important factor in the structuring and connectivity of fish stocks. Mark-recapture data, collected along the coastline of southern Africa from 1984–2015, were used to investigate the occurrence of different movement beh...
Article
Fisheries managers are increasingly promoting catch-and-release (C&R) to manage recreationally angled fish stocks. Despite this, there is a scarcity of information on the effects of C&R on estuarine-dependent species. Cape stumpnose Rhabdosargus holubi dominates the recreational fisheries catch and provides an important source of food for subsisten...
Article
Full-text available
Catch-and-release (C&R) is increasingly popular in recreational fisheries as it is thought to protect target species while still allowing anglers to continue recreational fishing activities. Several studies have highlighted high rates of mortality and many sub-lethal effects which ultimately have a negative impact on fish population viability. With...
Article
ABSTRACT While acoustic telemetry (AT) has become the dominant technique for understanding patterns of fish migration, catch rate (CR) and conventional tagging (CT) techniques still play a major role, particularly in developing countries. Understanding the potential biases of each technique is important for fish migration research. We compared thes...
Article
Full-text available
Connectivity — movements of animals between and among numerous habitats — and the factors (rhythmic cycles and environmental variables) influencing connectivity of juvenile Lichia amia (Teleostei: Carangidae) were assessed in complementary acoustic telemetry studies in two geographically separated estuaries (620 km apart) in South Africa. The studi...
Article
Full-text available
A total of 141 Polydactylus quadrifilis were sampled from the Kwanza Estuary in Angola ranging in size from 436 to 1360 mm fork-length (FL). Of these, 124 were male, six intersex and 11 female. Female fish were significantly longer (mm, FL) and heavier (kg) than males and had significantly higher gonadosomatic indices (GSI’s) than those of males an...
Article
The Kariega Estuary in South Africa, is an example of a freshwater-deprived estuary. Large-scale water abstraction and droughts have resulted in this estuary either being uniformly marine or hypersaline. A major episodic flood event in October 2012, the largest ever recorded in this system, provided us with an opportunity to investigate the prolong...
Article
Full-text available
Freshwater inflow has a strong impact on the biological, chemical and physical characteristics of estuaries, which in turn affect the distribution and abundance of estuarine organisms. Increased climatic variability associated with climate change is predicated to modify precipitation patterns, which will likely intensify floods in estuaries. The de...
Article
The Acoustic Tracking Array Platform (ATAP) is a marine science programme that monitors the movements and migrations of inshore marine animals along the South African coastline. Acoustically tagged animals are monitored by an expanded network of approximately 100 automated data-logging acoustic receivers moored at strategic node sites, from Cape Po...
Article
Understanding movement behaviour is essential for effective management of fishery species. Dart tags were used to study coastal movement patterns of white steenbras Lithognathus lithognathus, an overexploited seabream (Sparidae) in South Africa. In total, 6 962 fish (190–1 080 mm fork length) were tagged throughout the species’ distributional range...
Article
Full-text available
A total of 21 juvenile Cape stumpnose (Rhabdosargus holubi) were tagged with internal acoustic transmitters in the lower, middle and upper reaches of the Kowie Estuary, South Africa. The movements of all fishes were continually monitored for five months using 22 stationary data-logging acoustic receivers, positioned along the length of the estuary....
Article
Full-text available
Elemental analysis of biological calcified structures (e.g. fish otoliths, mollusc shelves, coral skeletons or fish and shark bones) provides invaluable information regarding ecological processes for many aquatic species. Despite this importance, the reduction of the raw data obtained through Laser-ablation Inductively Coupled Plasma Mass Spectrome...
Article
Full-text available
Understanding the level of connectivity between estuarine and coastal waters is essential for appropriate management of estuarine-associated taxa. Most studies have focused on the role of a single estuary, while limited research exists on the importance of multiple estuaries to individuals of estuarine-associated species. This study used acoustic t...
Article
Full-text available
Understanding and characterising movement and area-use patterns of fishes within estuaries, as well as understanding the degree of connectivity between estuaries and the marine environment, can provide important insights into a species’ ecology, which is fundamental for effective management and conservation. Mark-and-recapture data obtained from th...
Article
Full-text available
There is a growing need to incorporate biotic interactions, particularly those between predators and their prey, when predicting climate-driven shifts in marine fishes. Predators dependent on a narrow range of prey species should respond rapidly to shifts in the distribution of their prey, whereas those with broad trophic adaptability may respond t...
Article
Long-term home-range and movement dynamics of spotted grunter Pomadasys commersonnii and the distribution of their dominant prey, the sandprawn Callichirus kraussi, were investigated in the intermittently open East Kleinemonde Estuary, South Africa. In addition, the effects of fish length, diel cycle, season and other abiotic factors on home range...
Article
Full-text available
Habitat connectivity is a fundamental component of estuary-associated fish behaviour. Understanding this is critical to understanding population dynamics and the nursery role of estuarine habitats. This study aimed to elucidate the intra-population structure of juvenile Argyrosomus japonicus and the role of estuarine and coastal habitats for this w...
Article
The objectives of this study were to describe movements and area use patterns of largemouth bass Micropterus salmoides in relation to abiotic factors (water temperature, river inflow and water level). The study was conducted in the Kubusi arm of Wriggleswade Dam, Eastern Cape, South Africa where nine largemouth bass (310–385 mm FL) were surgically...
Article
Full-text available
This study provides empirical data on the exploitation of fishery resources on the Sundays Estuary on the south-east coast of South Africa. Total annual effort was estimated at 63 785 angler-hours, which accounted for an annual yield of 16 214 fish (8.0 t). Effort and mean catch per unit effort exhibited seasonal trends and were highest during summ...
Article
Full-text available
The movement behaviour of juvenile dusky kob Argyrosomus japonicus (n = 25) was studied in the 12 km long Great Fish Estuary, South Africa, by collecting telemetry data in relation to tidal conditions over 6.5 mo. Two behavioural patterns were observed. Tagged fish either moved in circatidal rhythms over long stretches up and down the estuary, corr...
Article
Full-text available
Acoustic telemetry and long-term seine-netting data were used to assess distribution, area use, home range dynamics and movement patterns of estuarine-dependent juvenile white steenbras Lithognathus lithognathus in the temporarily open/closed East Kleinemonde Estuary. Using 15 years of biannual seine-netting data, it was shown that white steenbras...
Article
Biotelemetry is an increasingly popular and effective tool to study fish movements. Interpretation of the results relies on the assumption that fish behaviour and physiology is not affected by the presence of the tag. Although the long-term effects of tagging should be evaluated before field telemetry studies, this has rarely been quantified. As a...
Article
The spatial dynamics and home range sizes of early juvenile white steenbras (Lithognathus lithognathus Cuvier, 1829) in the permanently open Great Fish Estuary, South Africa, were assessed using acoustic telemetry. Seven individuals (154–184 mm fork length) tagged with acoustic transmitters spent the majority of their time in the mesohaline to olig...
Article
The spatial dynamics and home range sizes of early juvenile white steenbras (Lithognathus lithognathus Cuvier, 1829) in the permanently open Great Fish Estuary, South Africa, were assessed using acoustic telemetry. Seven individuals (154–184 mm fork length) tagged with acoustic transmitters spent the majority of their time in the mesohaline to olig...
Article
Abstract  The characteristics and contribution of a developing recreational fishery to the local, regional and national economy of Angola were evaluated in 2006. Annual angling effort was 13 435 h, while the estimated total catch of the three target species [leerfish, Lichia amia (L.), west coast dusky kob, Argyrosomus coronus (Griffiths & Heemstra...
Article
Abstract The home range and area use of spotted grunter, Pomadasys commersonnii (Haemulidae) (Lacepède), were investigated in the Great Fish estuary, South Africa. Forty individuals (263–698 mm TL) were surgically implanted with acoustic-coded transmitters and manually tracked during two periods in 2003. Tagged fish spent on average 68 and 77% of t...
Article
The spatial and temporal area-use patterns of estuarine-dependent juvenile dusky kob Argyrosomus japonicus in the Great Fish Estuary, South Africa, were examined using acoustic telemetry. In all, 29 individuals (307-400 mm total length) were surgically equipped with individually coded transmitters and monitored for a period of up to 195 days using...
Article
Telemetry methods were used to investigate the influence of selected environmental variables on the position and movement of an estuarine-dependent haemulid, the spotted grunter Pomadasys commersonnii (Lacepède 1801), in the Great Fish Estuary, South Africa. Forty individuals (263–698 mm TL) were surgically implanted with acoustic coded transmitter...
Article
Full-text available
The coastline of southern Angola is sparsely populated and, largely because of a protracted civil war, has very lightly exploited inshore fish stocks. This has provided the almost unprecedented opportunity to determine prefishing-state reference points and to implement management strategies at the early stages of exploitation. The leerfish Lichia a...
Article
Factors influencing estuarine use and marine excursions by spotted grunter Pomadasys commersonnii in the Great Fish Estuary, South Africa, were studied using manual and automated telemetry methods. In all, 20 individuals, ranging from 362 mm to 698 mm total length (TL), were caught and tagged with acoustic-coded transmitters in the estuary. Tagged...
Chapter
Full-text available
The purpose of this study was to test the hypothesis that an estuarine species as the spotted grunter Pomadasys commersonnii is evenly distributed within the estuary and uniformly exploited by different groups of fishers. This was done by investigating the movements and area use of spotted grunter in relation to the fisheries. The position of 20 ac...
Article
Full-text available
The principal objective of this thesis was to gain an understanding of the movement patterns of spotted grunter Pomadasys commersonnii, an estuarine-dependent fishery species, in the turbid, freshwater dominated Great Fish Estuary. Both manual and automated telemetry methods were used to monitor the movements of spotted grunter during two separate...

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Projects (5)
Project
In a human-altered marine environment, fragmented and subjected to unprecedented climate change, planning sustainable strategies for development requires to understand the distribution of marine biodiversity and how its variations impact ecosystem functioning and the evolution of species. Functional Connectivity characterizes the migratory flows of organisms in the landscape. As such, it determines the ecological and evolutionary interdependency of populations, and ultimately the fate of species and ecosystems. Gathering effective knowledge on Marine Functional Connectivity (MFC) can therefore improve predictions of environmental change impacts and help refine management and conservation strategies for the Seas. This is challenging though, because marine ecosystems are particularly difficult to access and survey. Currently, >50 institutions investigate MFC in Europe, by using complementary methods from multiple research fields to describe the ecology and genetics of marine species. SEA-UNICORN aims at coordinating their research to unify the varied approaches to MFC and integrate them under a common conceptual and analytical framework for improved management of marine resources and ecosystems. For this, it will bring together a diverse group of scientists in order to collate existing MFC data, identify knowledge gaps, reduce overlap among disciplines, and devise common approaches to MFC. It will promote their interaction with connectivity theoreticians and ecosystem modelers, to facilitate the incorporation of MFC data into the projection models used to identify priorities for marine conservation. Lastly, it will forge strong working links between scientists, policy-makers and stakeholders to promote the integration of MFC knowledge into decision support tools for marine management and environmental policies.
Project
The aim of this study is to collect national biological data on O. conwayi by initiating a citizen science program incorporating South Africa’s recreational spearfishers.
Project
This study aims to both identify critical settlement habitats (unvegetated) for coastal fish species as well as to demonstrate that adjacent vegetated habitats are linked through similar species utilization thus providing an important seascape nursery.