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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