Temporal and Spatial Distribution of Fish Larval Assemblages of the Tebrau Straits

South Western Johore Peninsular Malaysia

By

A. Arshad, Roushon A., S K Daud & Mazlan A G Department of Biology

Faculty of Science, UPM

Email: azizar@fsas.upm.edu.my

Biological and ecological information on fish larvae is essential for fisheries management.

Spawning ground and spawning season could be determined based on the spatio-temporal larval distribution data

Temporal patterns of variation in the composition of assemblages can also be used to determine dynamics of recruitment patterns of fish.

Introduction

Objectives of the research

1. To establish the list of fish larvae found within the seagrass bed, mangrove, estuarine and open sea of the Tebrau’s Straits .

2. To determine the composition, abundance and distribution of fish larvae in the study areas.

Materials and Methods

Study area:

The Study were conducted in the Tebrau Straits. Five (5) stations were selected:

St.1 (N 010 23.345/; E 1030 36.741/), River Pendas

St.2 (N 010 22.790/; E 1030 38.140/), R. Pendas Estuary

St.3 (N 010 21.597/; E 1030 37.491/), Straits/ Mangrove

St.4 (N 010 19.414/; E 1030 35.628/), Seagrass bed

St.5 (N 010 18.799/; E 1030 35.246/), Open seas

Each sampling station is approximately 1 km apart from each other (Fig.1)

Sampling:

Monthly sampling ‘was carried out during full moon/new moon period, at both high and low tides.

Samples of fish larvae were collected using Bongo net (Fig.2) through 30 min subsurface net towing.

A flowmeter is attached to the net in order to determine the volume of the water filtered.

Sampling period: October 2007 to March 2008

Habitat Parameters

At each sampling station, the following environmental parameters are being obtained by YSI multiparameter recorder:

Temperature (0C)

Dissolved oxygen (mg/L)

Salinity (ppt)

PH

Total dissolved solid (mg/L) &

Conductivity (mS/cm)

Sample Processing:

After each tow, samples were immediately fixed in 5% formalin and transported to the laboratory for further analysis.

Samples were sorted out to family level, taxonomically identified and permanently stored in 75% alcohol.

Identification to the family level using the appropriate literatures (Leis and Carson-Ewart, 2000; Kawaguchi, 2002)

Composition & Distribution

In the laboratory fish larvae were sorted from the rest of zooplankton.

Numerical estimation of larval abundance of different families were counted using a dissecting microscope.

Results

Environmental Parameters: Site Analysis

Mean ± SD of the environmental parameters from the different stations were calculated and from the analysis of variance (ANOVA) stated that there were significant differences (P < 0.05) among the five stations (Table 1)

Environmental Parameters: Tidal Analysis

Mean ± SD of the environmental parameters during low tide and high tide were also calculated and showed significant differences (P < 0.05) (Table 2)

Species Composition and Abundance

A total of 34 families were identified. From these, 16 occurred in River, 22 in Estuary, 19 in Strait, 22 in Seagrass bed and 14 in Open sea. Among the 34 families, 13 families are commercially important (Table 3).

Overall, 5 families (Clupeidae, Blenniidae, Sparidae, Gobiidae and Sillaginidae) were the most common in term of numbers in the study areas.

Some Photographs of Fish Larvae

Cynoglossidae, 50x Clupeidae. 40x Tetraodontidae, 50x

Triacanthidae, 40x Monacanthidae, 50xLeiognathidae, 100x

Blenniidae, 50x Cynoglossidae, 45x

Belonidae, 50x

Syngnathidae, 25x

Gobiidae, 50x

Samaridae, 50x

Unidentified, 100x

Sillaginidae, 50x

Unidentified, 50x

Abundance and Spatial Distribution

The highest mean number (240.33 /unit effort) of fish larvae was found in the Merambong seagrass beds.

This was followed by the station 3 located in Tebrau Straits (fringed with mangroves) and lowest in the open sea area (Fig.4)

An analysis of variance (ANOVA) stated that there were significant differences between the stations on the basis of abundance of fish larvae (p < 0.05)

50.17

103.67

26.67

240.33

160

0

50

100

150

200

250

300

River Estuary Strait Seagrass Off shore

Study sites

Mea

n fis

h la

rvae

(nos

/uni

t eff

ort)

Fig.4. Spatial distn of fish larvae

Spatio-temporal Distribution

The highest number (1074/unit effort) of fish larvae was found during the month of February in Merambong seagrass bed. (Fig.5)

Lowest number of fish larvae (6/unit effort) was found during the month of October in the upper river station (Fig.5)

MONTH

Mar 08Feb 08Jan 08Dec 07Nov 07Oct 07

Ab

un

da

nce

(n

os.

/ un

it e

ffort

)1200

1000

800

600

400

200

0

Station

River

Estuary

Strait

Seagrass

Off shore

Fig.5. Temporal and spatial distribution of fish larvae

Correlation Betn Larval Abundance and Environmental Parameters

Parameters X Abundance

Correlation co-efficient (r)

Significance level at 5% level

Comment

Temp X abundance

-0.073 P> 0.05 Not significant

Sal X abundance 0.328 P> 0.05 Not significant

DO X abundance 0.192 P> 0.05 Not significant

Cod. X abundance -0.051 P> 0.05 Not significant

PH X abundance 0.212 P> 0.05 Not significant

TDS X abundance 0.318 P> 0.05 Not significant

There were no significant correlation between abundance of fish larvae and environmental parameters

• Lists of Fish larvae known to exist in the coastal waters of Gelang Patah, Johore have been established.

• A total of 34 different families were identified from the coastal waters of Tebrau Straits, Johore.

Summary of results

• The average highest number ( 240.33 /unit effort) of fish larvae was found in Merambong seagrass bed and lowest in the open sea.

• An analysis of variance (ANOVA) stated that there were significant differences between the stations on the basis of abundance

Summary of results

• Temporal variations were observed on the abundance of fish larvae, where the highest number (1074/unit effort) of larvae was recorded in the month of February in seagrass bed and the lowest number (6/unit effort) was found in October of River Pendas station..

• There were no significant correlation (P > 0.05) between the abundance of fish larvae and environmental parameters.

Summary of results

THANK YOU

FOR

YOUR ATTENTION

Fig.1. Geographical location and three sampling stations

Fig.2. Bongo Net (Mesh size 500 µm, mouth diameter 0.3 m and length 1.3 m )

Fig. 4. Photograph of YSI

St-1. River of Pendas

St-2. Estuary

St-3. Straits of Teberau

St-4. Seagrass area

St-5. Open Sea