
FIGURE 1. Location of sampling stations in Edremit Bay (Natural Reefs: S–1: Station
1, S–2: Station 2 and S–3: Station 3; Articial Reefs: S–4: Station 4 and S–5: Station 5)
Ichthyoplankton abundance in Edremit Bay / Zengin et al. __________________________________________________________________________
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INTRODUCTION
The studies on ichthyoplankton are important in the life cycle
of sh species and stock management. Quantitative studies have
found this important, explaining how sh species reproduce and
recruit in the aquatic ecosystem [1]. Additionally, water quality and
environmental conditions may affect the initial phases of the life cycle
of sh species [2]. Larval shes exhibit a high degree of fragility and
are particularly vulnerable to uctuations in environmental conditions
and water quality. Due to the fragility and sensitivity of larval sh to
ambient and water quality uctuations, any environmental impact
on these populations could be catastrophic [3]. The investigation of
ichthyoplankton in Edremit Bay has been limited and the main studies
so far being those by Türker–Çakır [2].
Edremit Bay is one of the important areas for small–scale shing in
the North Aegean Sea. For this reason, Türker–Çakır [2], suggests that
more detailed ichthyoplankton studies should be continued to evaluate
the sh stock status of the region, calculate the adult sh biomass,
and determine the spawning period, place, and time of sh species. In
addition, from 2011 to 2013 articial reefs were constructed in Edremit
Bay. This articial reef in Edremit Bay is one of the largest articial
reef areas in the Levantine basin. Regular research of sh eggs and
larvae in the region inuenced by Edremit Bay Articial Reef would
offer a better knowledge of the structure and function of the local
ecosystem, as well as provide a basis for marine ecosystem monitoring
in the area. The rst comprehensive ichthyoplankton study in the world
was carried out by Cunningham [4] on the coasts of England, while the
rst ichthyoplankton study in Turkey was carried out by Arım [5] and
included the descriptive characteristics of 8 species sampled from
Marmara and Black Sea. In many ichthyoplankton studies after this
date, species–specic early stages were investigated, while the number
of studies investigating habitats in terms of a time series, (e.g., Mater
[6], Çoker [7], Çoker and Mater [8]) as in the Gulf of İzmir is limited.
In addition, no ichthyoplankton monitoring study has been carried
out for articial habitats until this study. Ichthyoplankton surveys are
one of the most useful and reliable methods to observe changes in
sh communities [9, 10, 11, 12]. As a result, the current study intends
to report on the regional and temporal uctuations in the particular
composition and abundance of ichthyoplankton via a comparative
analysis of the data set. For this aim, samplings were carried out in 2013
(winter 2013), in 2014 (spring 2014; summer 2014; autumn 2014; winter
2014), in 2015 (spring 2015; summer 2015; autumn 2015; winter 2015),
and in 2016 (spring 2016; summer 2016; autumn 2016; winter 2016) in
Edremit Bay near the articial reef. However, in this study, only data
from 2015 and 2016 were evaluated.
MATERIAL AND METHODS
Edremit Bay is one of the greatest gulfs in the North Aegean Sea,
with a narrowest point of 34 kilometers and a widest point of 45
kilometers. Edremit Bay is topographically separated into two bays:
inner and outer bays. The inner bay is generated to the east of the line
formed by the underwater valley that generates the depth differences
between Bozburun and Altınoluk, while the outer bay is formed to
the west [13]. Edremit Bay is located in the mixing zone of waters of
Mediterranean and Black Sea origin. As a result of the mixing of these
water masses with two different salinity and temperature, upwelling
occurs with the effect of current systems. This situation causes an
explosion of phytoplankton and zooplankton in the region and creates
suitable habitats especially for pelagic sh [14, 15]. In addition to these
features, Edremit Bay was preferred for articial reef application due
to its suitable bottom structure. More than 6000 cylindrical articial
reefs made of C3 type concrete have been laid in the area close to
the coast from Narlı shores of Edremit Bay to Akçay shores. Samples
were collected from stations determined within this area (FIGURE 1).
A WP–2 type plankton net (57 cm diameter, 250 µm mesh size)
was used to collect data horizontally from the surface for 10 min at
a speed of 2 knots. Eggs, larvae and sh samples, physico–chemical
parameters and chlorophyll–a values were obtained from stations
belonging to two different habitats: natural reef and articial reef
in Edremit Bay in 2013 (winter 2013), in 2014 (spring 2014; summer
2014; autumn 2014; winter 2014), in 2015 (spring 2015; summer 2015;
autumn 2015; winter 2015), and in 2016 (spring 2016; summer 2016;
autumn 2016; winter 2016). However, in this study, only data from 2015
and 2016 were evaluated. Physico–chemical environment parameters
(depth, temperature, pH, salinity, dissolved oxygen) and chlorophyll–a
(chl–a) values were measured seasonally and in the eld at all stations
with a WTW Multi 340i model (made in Germany) portable parameter
measuring device. Station names, depths, temperature, salinity,
dissolved oxygen levels, and chl–a values were presented in TABLE I.
Ichthyoplankton were preserved in 4% buffered formaldehyde
solution. they were then separated and classied, with the help of the
stereoscopic microscope (4×10X) (Olympus SZ–60 type, Japan). Eggs
and larvae were identied following Mater [6], Çoker [7], Fahay [16],
Leis and Rennis [17], Leis and Trnski [18], and Moser [19]. The number
of ichthyoplankton individuals per 100 m
3
was computed using the
methods described by Postel et al. [20] and Çoker and Cihangir [3]:
V = t × v × M (m
3
/individuals = hour × mph × m
2
) where V = sampling
volume, t = sampling time, v = sampling velocity, and M = area of the
net mouth (M=π×r
2
). The abundance of the observed species was
calculated as follows:
Abundance = N/V (individuals/m
3
) where N = number of samples
from each station. The calculated result was then multiplied by 100
and reported as number of individuals per 100 m
3
[3]. The chi–square
test was applied to determine whether there is a difference between
stations and seasons in terms of the abundance of sh eggs and larvae.