International Journal of Marine Science, 2017, Vol.7, No.5, 37-50
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et al., 1999). The goatfish populations are fished by many countries among which is Egypt (in Red Sea) and Syria
(in Mediterranean Sea) from where the samples for the present study have been examined. The data on landed
catch of this species are not available in both Syrian and Egyptian coasts. However, the catch of this species has
contributed substantially to the total marine fish landings in Syria (Saad, 2010). Whatever so, the total marine fish
landings in Syrian coasts (from the Mediterranean Sea) have not exceeded more than 4000t for the last ten years.
Studies on genetic variability of
U. moluccensis
from the Red Sea and the eastern Mediterranean Sea (Golani and
Ritte, 1999; Hassan and Bonhomme, 2005) have found no genetic differences between these populations.
However, environmental factors such as water temperature, salinity, radiation, dissolved oxygen, water depth and
current flow have shown to cause variation in the morphology of the fish (Vladykov, 1934; Smith, 1966; Turan,
2000) even when no apparent differences are observed in the genotype (Imre et al., 2002). Morphological features
are continuous characters depicting the shape of the fish and hence their differences between populations remain
to have a valuable tool in fish stock identification (Sajina et al., 2011a; 2011b; Pazhayamadom et al., 2015). Stable
shape differences in fish groups may reveal differential growth, mortality or reproductive rates, which are
parameters, used in many stock assessment models (Swain and Foote, 1999; Cadrin, 2000).
Fish stocks shown to be separated for a considerable period may show a notable morphological differentiation
within a species and such information can be used to determine the boundaries of unique fish stocks (Sajina et al.,
2011a; 2011b; Pazhayamadom et al., 2015). This information is important because it help us to understand their
reproductive behaviour (spawning migrations), feeding behaviour (migrations for food) and ontogenetic
development, thus explaining their connectivity between geographical habitats (Secor, 2004). Many analytical
models assume a closed life cycle for fish stocks where the individuals belong to unique spawning component
with homogenous vital rates. Therefore, ongoing management of exploited fish resources require information on
the spatial structure of fish populations (Cadrin and Secor, 2009). Such information can assist with designing the
sampling programs for population studies, developing management strategies and framing policies for long-term
fisheries sustainability (Pazhayamadom et al., 2015). However, management practices with inadequate knowledge
of the stock may bring substantial changes in the biology and productivity of fish populations (Altukhov, 1981;
Ricker, 1981).
In this study, we use morphometric analysis to investigate the stock differences of
U. moluccensis
populations
from two geographical regions i.e., the Red Sea and the Mediterranean Sea. Though the populations from both
locations have historically originated from the same genotype, differences in morphology may indicate the
existence of multiple fish stocks, particularly given the geographical separation and limited intermixing of
individuals for spawning purposes. We collected measurements on morphometric distances and processed them
using an allometric approach to remove the effect of size from shape of the fish. The resultant data was then
analysed using PCA and pattern recognition techniques to determine whether the populations belong to two
distinct fish stocks.
1 Materials and Methods
1.1 Sampling and data collection
A total of 100 specimens of
U. moluccensis
were collected from the catch landed by commercial fishing vessels,
50 each from the Red Sea coast at Hurghada, Egypt and the Mediterranean Sea coast at Latakia, Syria
(January-February and July-August, 2000) (Figure 1). These specimens are the same specimens that Hassan and
Bonhomme (2005) have collected. According to Reist’s recommendation (Reist, 1985), at least 25 animals should
be used for morphological analysis and hence the number of samples was assumed to be sufficient to explore the
differences between these populations. Bottom trawl net was used to catch the fish specimens at a depth range
10-120 m from both localities. Following capture, the samples were placed individually into plastic bags were
kept deep-frozen (-20
°
C) until further analysis. The identification of the species was based on Uiblein and Gouws
(2014; 2015), Uiblein and Heemstra (2010) and the features of the species were compared with the closely related
species (Table 1). In the laboratory, the specimens were allowed to thaw and the morphometric measurements
were measured using a digital caliper to the nearest 0.1 mm. A total of 14 morphometric distances were measured
