الفهرس 
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Abstract
Spinner dolphin (Stenella longirostris) is considered one of the
most worldwide distributed dolphins where they geographically
distributed in tropical and subtropical areas. Although, Egyptian coasts
of the Red Sea represent one of the most common resting areas for
spinner dolphin’s population, knowledge about their population
structure, occurrence, and biometrics is not clear especially.
Accordingly, the aim of this study is to investigate the population
structure of spinner dolphins at Satayah reef in relation to some
environmental variables. In addition, the study introduces a
preliminary perception on the impacts of dolphin watching activities
in the study area. Moreover, applying a laser photogrammetry
technique to describe the morphological characteristics, allometric
growth, growth rates, and sexual dimorphism of the studied
population. Finally, the study introduces, for the first time, a molecular
characterization of Stenella longirostris population at Satayah reef.
Population structure; including abundance, group age, and
occurrence of spinner dolphin, environmental variables; including sea
surface temperature, wind speed, wind direction, sea level height, and
cloud cover, and tourism activities; including number of boats and
zodiacs were monitored at Satayah Reef during October 2014 to April
2016. For biometric study, morphometric data (Total length (TL); tip
of upper jaw to apex of the melon (M1); tip of upper jaw to gape of
mouth (M2); tip of upper jaw to center of eye (E); tip of upper jaw to
anterior insertion of flipper (P); tip of upper jaw to tip of dorsal fin
(DF); max girth (MG); axilla girth (AG); dorsal fin base length (DFB)
and dorsal fin height (DFH); pectoral fin width (PB) and pectoral fin
length (PL)) were collected using paired-laser photogrammetry
English Summary
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technique from a sample of 64 spinner dolphins composed of 19 adult
females, 34 adult males and 11 calves collected from April 2015 until
April 2016. Furthermore, the genetic identity of the spinner dolphin
samples collected during 28 February until 28 April 2016 by using
biopsy pole system for the bow-riding dolphins at the study area were
resolved using COI molecular phylotyping technique.
Results showed that, out of 84 survey days of the whole study
period in Satayah Reef, spinner dolphins were sighted 78 days (93 %
of the total survey days). However, the population abundance
fluctuated non-significantly with months and seasons (one-way
ANOVA, P > 0.05). In general, the overall mean of the group size in
the study area was 57.4 ± 25.09 individuals. Calves were observed
through all the study period.
The birth season of spinner dolphin population in Satayah reef was
estimated. Mean number of pregnant females showed a seasonal
pattern, they start to appear at November, a sharp peak (3.50 ± 2.64
individuals) in June 2015, concurrently with the occurrence of
neonates (giving birth season which start at May until July) and then
they disappear suddenly together at the end of the giving birth season
on August. Occurrence of the neonates have a seasonal variability with
obvious trend.
Changes in the mean daily presence of the dolphins was not related
to the changes in the environmental variables (one-way ANOVA, P >
0.05). Statistically, number of zodiac and number of boats have no
effect on the dolphin’s abundance. However, the presence of tourists
showed an obvious effect on the behavior of the dolphins inside the
study area. The current study showed a fluctuation in their behavior
between avoiding and attracting to or from the snorkelers.
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In terms of morphometric data, out of 112 measurements for the
population of spinner dolphin, TL ranged from 61.65 to 174.85 cm.
Sexual size dimorphism was remarkable in most of the external
measurements (TL, DFH, DFB, PB, and PL) between the adult males
and females (one-way ANOVA, P<0.05). Male spinner dolphin was
larger in the most external measurements, excluding tip of upper jaw
to apex of the melon (M1); tip of upper jaw to gape of mouth (M2)
which were larger in adult females (one-way ANOVA, P<0.05).
All the linear body measurements of the measured body parts
exhibited a negative allometric growth (where b < 1). These
characteristics were compared with each other to estimate the
biometric relationships between the different body parts. As an
important morphometric characteristic, relationships between the total
length and the other body characteristics was compared. Nevertheless,
total length and other morphometric characteristics exhibited high
correlations in the regression equations where the coefficients of
correlation displayed high values of more than 0.9.
The growth rate was determined by tracking the increasing in the
total length (TL) of 6 calves, 6 adult males and 3 adult females during
the study period from April 2015 to April 2016. A comparative
analysis was conducted to estimate the differences in the growth rate
of the dolphins when there are mature and calves. The mean total
lengths of adult males and females increased by 1.48 ± 0.36 and 1.26
± 0.28 cm/year, respectively, while the total length (TL) of calves
increased by 47.82 ± 6.21 cm/year. Similarly, DF characteristic has a
high mean rate of 35.81 ± 8.83 cm/year in calves. Similar trend was
found for other morphometric characters such as PB and M1.
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The molecular analysis of Cox 1 indicated that S. longirostris at
Satayeh reef is genetically different from their relatives. The
phylogenetic analysis of COI sequences resolved by the current study
and that available at NCBI GenBank indicated that S. longirostris at
Satayeh reef form a unique and distinct population.
These morphometric results conclude that the total length
considered as a main morphometric character which can be used to
show the difference in lengths between the two sexes and through the
maturity stages.
Although, the positive initial response of the dolphin toward the
human but recently it can have a negative impact on dolphin fitness.
On the other hand, spinner dolphins are clearly easier to visit their
common resting areas e.g. Satayah reef than the other nearby reefs
along the southern Egyptian coast of the Red Sea. Despite of the
continuous presence of tourist. This showed that dolphins are used to
being vicinity of people than else where.