CRAMP RAT Other Fish SurveyTechniques

Numerous methods have been developed for sampling fishes. Method selection depends on the focus of the research and the spatial and temporal scales involved. Accuracy can depend on the number and size of transects and whether transect locations are randomly selected, stratified random (e.g. following depth contours), or fixed. Fixed transects may not be representative of the entire community of interest but allow for more accurate repeated measurements.

Visual fish censusing methods used in nearshore marine sampling
Method	Type	Description	Limitations
Presence/ Absence	Qualitative	Lists species	No abundance or density data
Timed Swim	Qualitative	Surveyor swims within defined area for specified length of time recording species observed	Records species only No size estimates
Relative Abundance	Semi-Qualitative	Records abundance of species	No density estimates
Reed Method (Reed 1980)	Semi-Qualitative	Surveyors record species only once, in the order they are sighted	No size estimates
Rapid Visual Transect (Sanderson and Solonski 1986)	Semi-Qualitative	Species are recorded only once and assigned to a time interval based on when they were observed	Underestimated patchy
Species Abundance	Quantitative	Records number of individuals and size	Time constraints
Line/Strip/Belt transect (Brock 1954)	Quantitative	Line laid prior to observations. Records number of individuals and size	Speed variability: rare and cryptic species overlooked, highly mobile species overestimated
Video Transect	Quantitative	Video recording	Limited resolution
Circular Plot	Quantitative	Visual or video recording of all fishes in a 360^o arc in a designated time period	Water visibility estimate necessary High variability

Spatial and temporal variability of fishes can be extremely high due to mobility and large home ranges. Many fish species are cryptic, rare or transient. There are also diurnal/nocturnal and seasonal sources of variability. To quantify absolute values for fish populations an extremely large sample size is required especially for heterogeneous habitats. Relative values are often used to determine differences between sites.

Our RATs species abundance estimates were selected to maximize data and statistical comparability, allow for length to biomass conversions, and avoid limitations inherent in some other methods. This method includes two measures of abundance: numerical and biomass. These are both important population parameters that address different aspects of fish community structure. Unlike the belt transect method, species abundance estimates do not require additional survey time to allow for fish equilibrium to occur. The transect line is spooled out as the survey is conducted to avoid fish dispersal. Although additional dive and training time must be allotted to estimate fish length, post processing of data is relatively rapid.

CRAMP Home

Long Term Monitoring

Rapid Assessment

Methods

Site Selection

Geographic Coordinates

Biological Parameters

Benthic Protocols

Fish Survey Techniques

Rugosity

Sediments

Environmental Parameters

Statistical Methods

Bio-Indicators

Results

Mapping

Watersheds

Publications

Search the CRAMP Website

Navigate the CRAMP Website

Bibliographic Search

CRAMP Rapid Assessment. Other Fish Survey Techniques