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THE EFFECT OF SIZE AND STRIPE LENGTH ON THE ATTRACTIVENESS OF LABROIDES DIMIDIATUS MODELS

Introduction

Bluestreak cleaner wrasse, Labroides dimidiatus, are obligate cleaners who receive nutrition from the removal of ectoparasites, mucus and dead tissue from their client fish. They are found around prominent features of the coral reef such as coral heads, tabulate coral and sand patches. L.dimidiatus attract client fish by performing a distinct zig-zag dance which often solicits a posing response from the client fish. L.dimidiatus possess a characteristic black lateral stripe extending from the caudal fin to the tip of the head. This stripe is common to many obligate cleaners and it has been suggested that it may be used by client fish to identify the cleaners (Côté 2000). It has also bee proposed that as such a variety of fish visit cleaner stations, monitoring of artificial cleaner stations could be used as a method of measuring species abundance and diversity.

 

Aims

To determine experimentally if:

  1. The lateral stripe present on L.dimidiatus is used by client fish as a recognition marker, labeling it as an obligate cleaner.
  2. The length of the lateral stripe or the stripes proportion in relation to the wrasse body length is the important factor in attracting client fish.
  3. Super sized L.dimidiatus attract clients depending on lateral stripe length and proportion.

 

Objectives

  1. Test the attractiveness of adult L.dimidiatus models to client fish, recording the number of posing fish, species of posing fish, size of posing fish and duration of pose.
  2. Test each of the eight different models for one hour at three similar sites
  3. Collect all data by recording the model and its surroundings on camcorder and analyzing data accurately on return from the field.

 

Methodology

Four life size models and four super sized models with varying stripe length were tested at three different sites on Hoga Island home reef for 65 minutes, allowing 5 minutes for fish to become accustomed to diver presence. The model cleaner wrasse was attached to a 30cm length of fishing wire and weighted to the bottom. The model was kept moving to simulate the zig-zag dance used by real L.dimidiatus to attract client fish. All observations were recorded using a Sony underwater camera attached to a tripod.

            During analysis of footage the level of interest of each individual fish was recorded along with fish species, duration of interest and length of fish. Also video footage was paused at ten minute intervals and number and species of fish recorded in order to obtain an estimate of fish abundance.

 

Preliminary results

Preliminary observations suggest that there is a possible correlation between stripe length and attractiveness of the life size L.dimidatus models. However there seems to be no noticeable difference for the different stripe lengths of the super size models. The full stripe length models receive a higher frequency of actual poses as opposed to just background interest.

 

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