CRAMP Home

Long Term Monitoring

Rapid Assessment

Methods

Site Selection

Geographic Coordinates

Biological Parameters

Environmental Parameters

Statistical Methods

Multivariate Statistics

Statistical Transformations

Fish Statistical Techniques

Bio-Indicators

Results

Mapping

Watersheds

Publications



Search the CRAMP Website

Navigate the CRAMP Website

Bibliographic Search

CRAMP Rapid Assessment.  Fish Statistical Techniques

An index of relative dominance (IRD) was generated by multiplying the frequency of occurrence of each fish species (%) on each transect by their relative biomass (%) and multiplying by 100 (Greenfield and Johnson 1990).

CRAMP transects were standardized to meet statistical compatibility requirements with RAT transects by randomly selecting one of the four 25 m transects at each station.

Minitab 13.0 was used to perform all univariate, formal statistical tests. Spreadsheet and relational database software were used to determine population characteristics including; dominant and rare species, biomass and abundance rankings, feeding guilds and endemism status.

A non-parametric Kruskal-Wallis test was applied to compare fishing pressure and target fish species. This test compares several populations of independent random samples, ranking responses and applying a one-way ANOVA to the ranks rather than to the original observations. A traditional ANOVA was rejected on the basis of non-normal data including strong outliers.

Target fish species were selected to include popular food fishes. The genera selected were Acanthurus, Aphareus, Cephalopholis, Caranx, Scarus, Chlorurus, Seriola, Sargocentron, Priacanthus, Kyphosus, Mullodicthys, Parupeneus and Decapterus. Degree of fishing pressure at each site was based on management protection status and subjective expert knowledge by coral reef biologists. Sites were placed into one of three levels of fishing pressure: high, medium and low.
A simple linear regression was used to predict herbivore abundance by macroalgal abundances.

Multivariate statistical analyses included the same procedures used in the analysis of benthic data with the exception of a non-metric, multi-dimensional scaling technique, used to identify groups of similar sites. Environmental variables were overlaid on the ordination to identify the factors and their directions that are most important in structuring of fish communities.

Last Update: 04/21/2008

By: Lea Hollingsworth

Hawai‘i  Coral Reef Assessment & Monitoring Program

Hawai‘i  Institute of Marine Biology

P.O. Box 1346

Kāne‘ohe, HI 96744

808-236-7440 phone

808-236-7443 fax

email: jokiel@hawaii.edu