An Estimation of the Fish Population of the Bay of Famagusta
Ata Atun
INTERNATIONAL
SYMPOSIUM
MARINE
TECHNOLOGIES AND
MANAGEMENT 
AN ESTIMATION OF THE
FISH POPULATION
OF THE BAY OF
FAMAGUSTA BASED
ON RECORDED
CATCH OF TRAWL
Assoc. Prof. Dr.
Ata ATUN
Assoc. Prof. Dr.
Deniz ÜNSALAN
Near East
University,
Faculty of
Maritime Studies
Nicosia, North
Cyprus 
1.
ABSTRACT  A
rough estimation
based on the
trawl catch of
fish for the bay
of Famagusta was
made. Trawl
fishing made by
traditional
wooden boats of
about 15 m.
length at 50100
m. depth on
courses parallel
to the coastline
was taken as the
basis of the
estimate. In
order to be
conservative, it
was assumed that
90 % of the fish
corresponding to
the trawl net
entrance area
escaped either
from the net
entrance or
through the
openings of the
net. The results
were extended to
estimate the
weightwise
population of
some of
commercially
important fish,
using a Rayleigh
distribution of
fish for various
depths. Although the fish population of coastal areas
are a subject of
discussion in
everyday life,
almost no
numerical
information
exists in the
literatüre. In
order to
estimate the
fish population
of the bay of
Famagusta at the
Eastern shore of
North Cyprus,
the recorded
daily catch of
trawl fishermen
were used,
covering the
years 19891995.
The periods are
from September
to May, a total
of 85 days per
year. Systematic
observations
conducted by the
first author[l]
indicated that
65 distinct
species existed
in the waters
indicated. A conservative approach for the estimation of
fish population
of selected
species was
used. The area
where the
sampling was
made is the
50100 m. depth
range. The
results were
extended to
cover the entire
depth range
where the
particular
species lived,
assuming a
Rayleigh
distribution of
fish population
on depth basis.
The estimate of
fish 
populatioıı is on
weight basis,
which can be
extended to
cover the total
number of fish
for the area in
question. It should be stressed that the term "fish"
refers to marine
animal forms
caught by the
trawl net that
are commercially
significant, not
to "fish" in
biological
sense. As can be
seen later,
shrimp
(crustacean) and
octopus,
cuttlefish and
squid
(cephalopod
molluscs) are
also refered as
fish. 3. EQUIPMENT USED A trawl arrangement with two doors at 40 m.
lateral distance
apart and a net
entrance of 15
m. was used. The
distance between
the doors and
the net entrance
was 120 m. Since
the trawl net
extended from
the bottom to
the surface, it
was deemed
reasonable that
the net swept
ali the depths
where the fish
could possibly
be. The general
sketch of the
trawl equipment
is shown in
Figüre 1. 

Fig 1 : Bottom
Trawl details 
The swept area
at any instant
is roughly a
trapezoid:

Defining an
"Escape factor",
f(e) as
the ratio of
number of fish
escaped to the
total number of
fish at the
trawl net
entrance area,
or by the escape
of smaller fish
through the net
openings, the
effective sweep
rate shall be:

The escape factor will be either through the
openings of the
net or from the
entrance of the
net. Based on
observations, a
value of 0.90
was assumed for
the escape
factor. The trawling speed was 2.5 knots throughout
ali the catches.
The trawling
routes were
almost parallel
to the
coastline,
covering an area
extending from
35° 04' 30" N to
35° 17' 24" N
and 33° 53' 24"
E to 34° 00' 00"
E (See the chart
at Figüre 2).
The total area
corresponded to
about 8 square
nautical miles.
At each sweep, a
straight stripe
of 27.5 m. wide
at 50100 m.
depth range was
assumed to be
swept and the
fish caught
represented 10 %
of the
population at
that stripe.

4 ANALYSIS OF FISHING
RECORDS
Total area
swept is:
BBased on the numerical values cited above, the following populations were found for the swept areas:

and a cumulative probability fiınetion
P(x)
given by:
Assuming that
the tabulated
depth range,
(0R) metres of
the particular
species accounts
for the 99 % of
the population,
i.e.,
P{R) =
0.99
(7)
it can be shown
that:
a = 0.33
R
(8)
Therefore, the
fish population
for the 50100
m. range
tabulated in
Table 2 above
represents the
proportion of
the total
population in
the area under
investigation
as:


It can be shown
that the 50m.100 m. depth range accounts for,
as in Table 3:
Table 3
The results can be extended to the fish population at the bay of Famagusta as shown in Table 4: Table 4

5 CONCLUSIONS AND
RECOMMENDATIONS FOR FURTHER
STUDY It was shown that the fish population at the
bay of Famagusta was
commercially significant. The
methodology can be extended to
the estimate of the fish
population of other areas.
However, crude approximations
were made for the estimation of
the amount. A more detailed
method of analysis taking the
inaccuracies of the estimations
into account can be developed:
More accurate values of "escape
factor", a different and more
accurate probability density
function for fish distribution
and the inaccuracies involved by
the unevenness of the bottom
slope and bottom nature are
recommended for further study. References 1.
Ata ATUN, Suna ATUN : "Research
on Fish Species at Turkish Republic of North Cyprus", Coordination
Meeting on the Fisheries of
T.R.N.C., 2223 March 1999,
Nicosia and Famagusta, North
Cyprus. 2.
AKŞIRAY, F. : "Sea Fish of
Turkey and Recognition Guide",
Publications of İstanbul
University Rectorate, No.: 3490,
1987 