A correction factor for, and its application to, visual censuses of littoral fish

Christensen, Marit; Winterbottom, Richard

doi:10.1080/02541858.1981.11447736

Cited by 35 publications

(38 citation statements)

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“…The presence of observer bias in visual survey data has been noted previously (Christensen & Winterbottom 1981, Sale & Sharp 1983, Sanderson & Solonsky 1986, Mapstone & Ayling 1993, but in general little or no effort has been made to reduce such bias through training (but see Bell et al 1985, St. John et al 1990, Samoilys 1992. Mapstone & Ayling (1993) and St.…”

Section: Discussionmentioning

confidence: 99%

Observer effects and training in underwater visual surveys of reef fishes

Aa¹,

Bd²

1997

Mar. Ecol. Prog. Ser.

146

107

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Visual survey techniques are used widely to estimate abundances of target organisms in terrestrial and aquatic environments. There are a number of methodological 'errors' in almost all applications of visual surveys. Given the dependence of all visual survey data on the skill and technique of the observer, one potentially important source of imprecision andlor bias is vanation among and within observers. In studies involving large amounts of fieldwork over great geographic range and many years, it is inevitable that observers will change from place to place and through time at any single site as they are replaced or gwn experience. We present the results of 3 observer tralningkalibration exercises that lnd~cate that observational studies in which multiple observers must be employed may be subject to considerable observer-related biases and imprecision. We found that careful training and calibration of observers ameliorated such effects for most taxa, but non-trivial levels of bias for some taxa and imprecision m estimates for several taxa remained even after thorough training. It is essential that the influence of observer bias and impreclslon be well documented in multi-observer monitoring studies, so that (spurious) patterns related to differences among observers can be distinguished from real spatial or temporal patterns in the environment.

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Section: Discussionmentioning

confidence: 99%

Observer effects and training in underwater visual surveys of reef fishes

Aa¹,

Bd²

1997

Mar. Ecol. Prog. Ser.

146

107

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“…Furthermore, the use of visual census may be very appropriate on easily accessible and highly impacted areas. These are non destructive, low cost, easy to conduct methods that may be replicated several times, at different locations for comparisons, providing an advantage for monitoring areas in which tourism and fisheries have already reduced fish populations (CHRISTENSEN & WINTERBOTTOM, 1981;ENGLISH et al, 1994;FERREIRA et al, 1995;WILLIS, 2001). …”

Section: Discussionmentioning

confidence: 99%

“…Visual census methodology was adapted from CHRISTENSEN & WINTERBOTTOM (1981) in respect to observation time, and consisted of an intensive species search, by snorkeling around the internal rim of the tidepool. Each full search lasted less than 25 minutes to avoid repetitive counts.…”

Section: Methodsmentioning

confidence: 99%

Comparative analysis of tidepool fish species composition on tropical coastal rocky reefs at State of Ceará, Brazil

Cunha

Carvalho

Monteiro‐Neto

et al. 2008

Iheringia, Sér. Zool.

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ABSTRACT. This study compared tidepool fish assemblages within and among habitats at Iparana and Pecém beaches, State of Ceará, Northeast Brazil, using visual census techniques. A total of 8,914 fishes, representing 25 families and 43 species were recorded. The most abundant taxon was Sparisoma spp, followed by Haemulon parra (Desmarest, 1823), Acanthurus chirurgus (Bloch, 1787) and Abudefduf saxatilis (Linnaeus, 1758). Haemulidae was the most abundant family in number of individuals, followed by Scaridae, Acanthuridae and Pomacentridae. Within-and between-site differences in species assemblages probably reflected environmental discontinuities and more localized features, such as pool isolation episodes, or environmental complexity, both acting isolated or interactively. The locality of Iparana was probably subjected to a greater fishing pressure and tourism than Pecém, a potential cause for the observed lowest fish abundance and biodiversity. We conclude that tidepool ichthyofauna may be quite variable between and within reef sites. Thus, observations taken from or damages caused on one area may not be generalized to or mitigated by the protection of adjacent sites. KEYWORDS.Visual census, fish assemblages, abundance, biodiversity.RESUMO. Análise comparativa da composição das espécies de peixes em poças de maré em recifes costeiros no estado do Ceará, Brasil. Este estudo comparou assembléias de peixe em poças de maré dentro e entre hábitats nas praias de Iparana e Pecém, estado do Ceará, nordeste do Brasil, usando técnicas de censo visual. Um total de 8.914 peixes, representando 25 famílias e 43 espécies foi registrado. Sparisoma spp. formaram o taxon mais abundante, seguido por Haemulon parra (Desmarest, 1823), Acanthurus chirurgus (Bloch, 1787) e Abudefduf saxatilis (Linnaeus, 1758). Haemulidae foi a família mais abundante em número de indivíduos, seguida por Scaridae, Acanthuridae e Pomacentridae. Diferenças encontradas nas assembléias de espécies provavelmente refletiram descontinuidades ambientais e aspectos mais localizados, como a ocorrência de isolamento das poças, ou complexidade ambiental atuando de forma isolada ou interativamente. A localidade de Iparana provavelmente foi submetida a uma maior pressão de pesca e turismo que Pecém, uma causa potencial para a menor abundância e biodiversidade de peixes observada. Concluímos que a ictiofauna de poça de maré pode ser variável dentro dos recifes e entre localidades diferentes. Assim, observações tomadas ou os danos causados em uma dada área não podem ser generalizados ou mitigados para a proteção de locais adjacentes. PALAVRAS-CHAVE.Censo visual, assembléias de peixe, abundância, biodiversidade.

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“…Fishes are important mobile inhabitants of rocky shores and, along the South African coast, there have been several studies on the fish communities inhabiting tidal pools and sub-tidal gullies, particularly in the Western and Eastern Cape (Christensen & Winterbottom 1981, Bennett & Griffiths 1984, Beckley 1985a,b, Bennett 1987, Smale & Buxton 1989, Prochazka & Griffiths 1992). By contrast, although the ichthyofauna of shallow littoral reefs off Durban has been studied by Berry et al (1982) and Fennessy et al (1998a,b) little has been published about tidal pool fishes along the KwaZulu-Natal coast.…”

Section: Introductionmentioning

confidence: 99%

Species composition and recruitment of tidal pool fishes in KwaZulu-Natal, South Africa

Beckley¹

2000

African Zoology

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Fishes occurring in a lower shore tidal pool near Durban, South Africa, were collected using rotenone at monthly intervals for a year. Eighteen teleost families and 50 lower taxa of fishes were recorded. Cryptic Tripterygiidae, Blenniidae and Gobiidae were particularly abundant while Pomacentridae, Acanthuridae, Serranidae, Sparidae and Labridae were recorded in lower numbers. Resident intertidal fishes recolonized the pool between monthly visits, with tripterygiids and gobies showing evidence for year-round recruitment of juveniles. Juveniles of more transient Indo-Pacific species recruited primarily during the summer months.

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A correction factor for, and its application to, visual censuses of littoral fish

Cited by 35 publications

References 0 publications

Observer effects and training in underwater visual surveys of reef fishes

Observer effects and training in underwater visual surveys of reef fishes

Comparative analysis of tidepool fish species composition on tropical coastal rocky reefs at State of Ceará, Brazil

Species composition and recruitment of tidal pool fishes in KwaZulu-Natal, South Africa

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