EFFECT OF SEAWEED FARMING ON MACRO FAUNA SPECIES COMPOSITION IN BAGAMOYO

Title: Effects of Seaweed farming on Macrofauna species composition in Bagamoyo

 NAME: Mlay Francis Gasper

SUPERVISOR: Dr. A. MWANDYA

June 2013

INTRODUCTION

Seaweed farming is the cultivation of any seaweed species in an authorized specified area by any method with appropriate intensive care for production in commercial quantities.

Seaweed farming has been developed as an alternative to improve economic conditions and to reduce pressure and over exploitation on other resources.

Seaweeds farms are generally located in shallow, calm and constantly warm water where the bottom is sand.

INTRODUCTION CONT……………

Seaweed farming is practiced using a very diverse

range of farming methods that interact with the

environment in different ways.

The interaction depend on the method of farming, the

surface area of the farm and the site.

STATEMENT OF PROBLEM

Seaweed farming has expanded rapidly over the past few years.

This expansion has brought benefits in terms of income, employment and foreign exchange.

Despite the rapid expansion; there are still insufficient information on the ecological and environmental impact of seaweed farming on macrofauna species composition in Tanzania.

This is because, site preparation, farming methods, harvesting and other anthropogenic activities may have negative effects on macrofauna species composition.

JUSTIFICATION

Findings from this study will provide baseline

information on;

macrofauna species abundance, distribution,

composition and diversity.

Effect of seaweed farming on species of macrofauna.

Species of macrofauna found along Bagamoyo area.

OBJECTIVES

General objectives-To determines the effect of seaweeds farming on macrofauna

species composition in areas with and without seaweeds farming activities.

Specific objectives-To determines the abundance and distribution of macrofauna in

areas with and without seaweed farms.

-To determines the diversity of macrofauna in areas with and without seaweed farms.

HYPOTHESIS

Null hypotheses

There is no significance different in macrofauna species

composition, abundance and diversity between areas

with & without seaweeds farms.

MATERIAL AND METHODS

Study area

• Sampling site was Mbegani which is located in Bagamoyo district

• Bagamoyo is located at Latitude 6o 26o’S and Longitude 380

54oE.

– It lies 75km north of Dar es Salaam on the coast of Indian

Ocean, close to the island of Zanzibar.

DATA COLLECTION

-Data were collected from four sites (2 with seaweed farming and 2

without seaweed farming).

-A 1m2 quadrat was used to collect all slow moving macrofauna and

for those attached to the substrate or sessile organisms;

photographs and visual observation were carried out.

• Species identification was done in the laboratory at SUA using a

Field Guide to the seashore of Eastern Africa (Richmond, 2002).

.

Macrofauna species composition• Were determined by counting and identification of each group

in a given area according to Richmond, 2002.

Species abundance and distribution• Abundance and distribution were obtained by dividing the

proportion of individuals of a given species by the total area of the quadrant as described by Shannon &Weaver (1949).

Diversity of macro fauna species• Diversity was calculated according to Shannon-Wiener Index

(1963) i.e. H’= - (∑PiInPi)

Where pi = the proportion of individuals of species i.

DATA ANALYSIS

• Variations in abundance of macro fauna among the sampling

areas were statistically analyzed using Statistical Package for

Social Science (SPSS).

• Diversity index of macro fauna were obtained by using Shannon

Weiner index.

RESULTS

Species of macrofauna recorded

• A total of 7 families representing 9 species of macofauna were

recorded in both sites (Table 1).

• The most frequently observed macrofauna species in seaweed

farms were Penaeus monodon followed by Callinectes

sapidus, Penaeus indicus.

• Non seaweed farms were dominated by Penaeus indicus,

Penaeus monodon followed by Callinectes sapidus,

Clibananarium danai, (Fig. 1).

SW NSWFAMILY SPECIES TN AB/m2 TN AB/m2

Diogenidae Clibanarium danai 7 1.75 24 6.00

Clibanarium longitarsus 6 1.15 16 4.00

Penaeidae Penaeus indicus 29 7.25 94 23.5

Penaeus monodon 60 15.00 84 21.00

Pinnidae Atrina vexillum 3 0.75 16 4.00

Portunidae Callinectes sapidus 35 8.75 71 17.8

Loliginidae Loligo duvaceli 5 1.25 5 1.25

Holothuriidae Holothuria scabra 9 2.25 15 3.75

Cardiidae Plagiocardium pseudolima 5 1.25 3 0.75

Tatal 159 39.4 328 82.00

Table 1. Total number (TN) and abundance (AB) of macrofauna species in area with seaweed(SW) and without seaweeds farming (NSW) respectively.

Figure 1. Total number of macrofauna species in area with seaweeds (SW) and without seaweeds (NSW) farming.

Atrina

vexil

lum

Cliban

arium

dana

i

Cliban

arium

long

itursu

s

Calline

ctes s

apidu

s

Penae

us in

dicus

Loligo

duva

celli

Penae

us m

odon

Plagica

rdium

spp

Sea cu

cumbe

r0

10

20

30

40

50

60

70

80

90

100

SW

NSW

Species

Nu

mb

er o

f in

div

idu

al/a

rea

Macrofauna species abundance

• A total number of individuals were159 to 328 individuals from

seaweed and without seaweed farming respectively (Table1).

• Macrofauna were more abundant in area without seaweed

farms than in area with seaweed farms (Fig 2).

• Mcrofauna abundance showed significance difference between

stations (p < 0.05).

• The higher abundance in nonseaweed site indicates that

seaweeds farming activities have negative effects on

macrofauna abundance.

Atrina ve

xillu

m

Clibanariu

m danai

Clibanariu

m longitu

rsus

Callinec

tes sa

pidus

Penaeu

s indicu

s

Loligo d

uvace

lli

Penaeu

s modon

Plagio

card

ium p

seudolim

a

Holoth

uria sc

abra0.00

5.00

10.00

15.00

20.00

25.00

SW

NSW

Species

Ab

un

dan

ce/q

uad

aran

t

Figure 2. Macrofauna species abundance in areas with seaweeds (SW) and without seaweed (NSW) farming.

Macrofauna species diversity

• There was slightly higher diversity of macrofauna in areas

without seaweed farming (Table 2).

• The Shannon-Weaver diversity index (H′) of macrofauna was

1.73 and 1.75 in areas with and without seaweed farms

respectively.

SW NSW

TN Pi InPi H'= -∑PiInPi TN Pi InPi H'= -∑PiInPi

3 0.02 -3.91 0.08 16 0.05 -3.00 0.15

7 0.04 -3.22 0.14 24 0.07 -2.66 0.19

6 0.04 -3.21 0.12 16 0.05 -3.00 0.15

35 0.22 -1.51 0.33 71 0.22 -1.51 0.33

29 0.18 -1.71 0.31 94 0.29 -1.24 0.36

5 0.03 -3.51 0.11 5 0.02 -3.91 0.06

60 0.38 -0.97 0.37 84 0.26 -1.35 0.35

5 0.03 -3.51 0.11 3 0.01 -4.61 0.04

9 0.06 -2.81 0.16 15 0.05 -3.00 0.14

159 1.73 328 1.75

Table 2. Macrofauna species diversity in area with seaweed (SW) and without seaweed (NSW).

DISCUSSION

• Macrofauna species number were significantly lower in seaweeds farms than in unfarmed station which could be caused by several activities which are conducted in farming sites such as ;– removal of all grasses and unwanted seaweeds from the

area, removal of the rocks, stones, starfishes, sea urchins and other predators.

– physical removal of the macrofauna particularly shellfish, as some of them are used as food.

– construction of different structure for growing seaweeds, all of which could affects the distribution of macrofauna species.

back and forth movement of farmers in the seaweed farms and boat anchoring (while harvesting seaweeds) also may affect macrofauna composition.

The results shows that the seaweed farming activities have

negative effects on the macrofauna species associated with

seaweeds.

All these activities may contribute to the loss of diversity and

abundance of the macrofauna to the areas where they inhabit.

• However, more data of long term are required to evaluate the

damage that may be caused by seaweed farming on

macrofauna using both methods. With such information

sustainable management strategies can be designed.

CONCLUSION AND RECOMMENDATION

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