International Journal of Marine Science 2015, Vol.5, No.13, 1-11
8
2.5 Variation in the population and sequence of
appearance of species
In February, the first month of the study, 52
individuals made up of 10 species were recorded.
Macoma cumana
contributed 16;
T. fuscatus
, eight
individuals;
Tellina nymphalis,
seven individuals;
Clibanarius africanus,
six individuals;
P. aurita
, five
individuals;
Aloidis trigona
, four individuals; two
individuals each of
Neritina kuramoensis
and
Penaeus
notialis
were recorded, while a single individual each
of
Callinectes amnicola
and
Nereis
were recorded. In
the second month, total number of individuals observed
in the cages increased to 60, while the number of
species recorded increased to 15. All the species
recorded in February except the polycheate worm
N.
succinea
were also found in March.
Mytilus edulis,
Lumbrinerides
cingulata,
Nereis lamellose,
Neritina
glabrata,
Sesarma huzzardi
and
N. diversicolor
made
their first appearances in March. Major contributors to
the population invertebrates recorded in March include
M. cumana
(11 individuals),
T. fuscatus
(10),
P. aurita
(8),
Clibanarius africanus
(7) and
T. nymphalis
(6).
Fourteen species were recorded in April.
Nertina
glabarata
,
S. huzzardi
and
C. amnicola
were absent in
all the Cages in April. Species of importance in terms
of number include,
P. aurita
(17),
M. cumana
(13) and
T. fuscatus
(11). Of all the species recorded in this study,
only one (
S. huzzardi
) did not occur in all the cages in
May, while four (
A. trigona, N. glabarata,
Lumbrinerides cingulata
and
Nereis succinea
) of the
species were not observed in July.
2.6 Functional Feeding Groups
Four major FFGs were identified from the colonizing
species recorded in this study, these include; collector
- filterers (CF), collector - gatherers (CG), Predators
(P) and Shredders (S). Analysing the functional
composition of the assemblage, it was revealed that
CF were the most abundant FFG in the five
experimental cages accounting for 69.92 %, 70.83 %,
74.3 %, 71.43 % and 68 % of the total population of
colonizing individuals in cages 1, 2, 3, 4, and 5
respectively (Table 4). With a total 228 individuals,
CF accounting for 70.35 % of the animals recorded in
this experiment. Collector gatherers constituted
18.53 %, 8.33 %, 8.51 %, 8.16 % and 27.12 % in
cages 1, 2, 3, 4, and 5 respectively. Shredders were
also recorded in all the experimental cages, the group
comprised 13.53 %, 17 %, 17.14 %, 8.16 % and 4.4 %
of population of organisms recorded in cages 1, 2, 3, 4,
and 5 respectively. The Predator
L. cingulata
was
observed only in cage 4 where in constituted 8.16 %
of the total population of organisms in that cage.
Table 4 Number of individual representation of functional feeding groups in experimental cages. P = Predator; S = Shredder; CF =
Collector - Filterer; CG = Collector - Gatherer
Species
FFG
Cage 1
Cage 2
Cage 3
Cage 4
Cage 5 Overall % relative contribution
Pachymelania aurita
CF
23
5
7
6
15
17.28
Macoma Cumana
CF
39
8
5
3
6
18.83
Tellina nymphalis
CF
10
6
1
7
8
9.88
Aloidis trigona
CF
6
-
1
3
-
3.10
Mytilus edulis
CF
2
-
2
2
-
1.85
Sesarma huzardi
CF
1
1
-
-
1
0.93
Clibanarius africanus
CF
6
8
3
6
10
10.12
Callinectis amnicola
CF
1
-
-
3
-
1.23
Penaeus notialis
CF
5
6
7
5
-
7.10
Tympanotonus fuscatus
CG
24
4
3
4
16
15.74
Lumbrinerides cingulata
P
-
-
-
4
-
1.23
Nereis lamellose
S
2
3
-
2
-
2.16
Nereis diversicolor
S
2
5
4
2
1
4.32
Nereis succinea
S
-
1.54
Neritina glabarata
S
2
-
-
-
1
0.93
Neritina kuramoensis
S
10
-
2
-
-
3.7
