Vol.4, No.8, 517-525 (2012) Natural Science http://dx.doi.org/10.4236/ns.2012.48069 Fish assemblages in seagrass habitat along the Jordanian coast of the Gulf of Aqaba Maroof A. Khalaf1*, Saber Al-Rousan2, Fuad A. Al-Horani1 1Department of Marine Biology, Faculty of Marine Sciences, The University of Jordan-Aqaba, Aqaba, Jordan; *Corresponding Author: [email protected] 2Marine Science Station, The University of Jordan, Aqaba, Jordan Received 27 May 2012; revised 30 June 2012; accepted 10 July 2012 ABSTRACT completion of the full life cycle, a temporary nursery area for the successful development of the juvenile The spatial distribution and community struc- stages, a feeding area for various life stages and/or a ture of the fishes were studied at different refuge from predation [1,2]. The seagrass beds in the Red depths and sites along the Jordanian coast in Sea are found from mid-tidal level, on shores receiving seagrass habitat. A total of 37,034 fishes were regular tides, to about 70 m depth [3]. They tend to be counted representing 132 species belonging to concentrated in shallow water areas such as lagoons, 35 families observed during visual census in sharms (drowned wadi mouths), and mersas (shallow three sites (average of 4741.6 fish per transect). embayments) because of the soft-bottom sediments Out of the 132 species encountered, 5 species of found in these areas [4]. The seagrass, Halophila stipu- them including Neopomacentrus miryae Lethri- lacea has been described as generally having a wide nus borbonicus, Pseudanthias squamipinnis, ecological range, growing from intertidal to depths of Lethrinus variegatus, Siganus rivulatus ac- greater than 50 - 70 m [5-8]. Eleven species of all the counted for 57.7% of all individuals. Fishes were seven known genera of seagrass have been reported in most abundant and significantly higher at 12 m the Red Sea [4]. Out of the six species reported in the depths (mean N = 2889.6) in comparison with Gulf of Aqaba, only Halophila stipulacea, Halophila shallow 6 m depth (mean = 1225.3 with (p = ovalis and Halodule uninervis were found at the extreme 0.0218). This may be attributed to many plank- northern end of the Gulf of Aqaba [9,10]. They serve as tivorous fishes that inhabit this depth such as P. important nursery grounds for fish larvae and hosts sea squampinnis, Paracheilinus octotaenia, Chromis urchins and sea cucumbers [11]. In general, the commu- pelloura, Decapterus macarellus, and Cirrhila- nity is structurally and functionally complex. brus rubriventralis probably with high abun- The Red Sea Ichtyofauna is quite well known com- dance of plankton at 12 m depth than 6 m. The pared to other parts of the tropical Indo-Pacific Ocean. number of species was significantly higher in About 507 fish species have been recorded in the Gulf of Phosphate Loading Berth (PLB; mean S = 54.7) Aqaba [12]. The number of fish species recorded in the than in Hotels area site (HA; mean S = 12.8) with Red Sea is about 1300 [13]. [14] reported Novaculichthys (p = 0.0002) and Tala Bay site (TB; mean S = 31) macrolepidotus as a new record from the Gulf of Aqaba with (p = 0.0484). This may be due to higher hard inhabiting a seagrass Halodule uninervis at 2 m depth. coral cover at Phophate Loading Berth. During the last four decades, the coral reefs of Aqaba and Eilat undergone major changes resulting from in- Keywords: Fish Assemblages; Seagrass Habitat; creasing impacts due to human activities [15,16]. Rapid Gulf of Aqaba; Red Sea developments in Aqaba city during the past few years have identified the pressure on coral reefs and seagrass 1. INTRODUCTION habitat including phosphate loading berth, toursistic pro- jects, ports relocation and other anthropogenic activities. Seagrass beds are presumed to have a fundamental The objective of this study was to carry out a thorough role in maintaining fish populations by providing one or fish survey at various sections of the Jordanian Gulf of more of the followings: a permanent habitat, allowing Aqaba within an area distinguished for its seagrass. The Copyright © 2012 SciRes. OPEN ACCESS 518 M. A. Khalaf et al. / Natural Science 4 (2012) 517-525 main aim of this study was to describe the fish commu- observer swam along the transect and recorded all fishes nity structure in the area. encountered within 2.5 m on each side of the line and 5 m above transect. The duration for the fish count on each 2. MATERIAL AND METHODS transect was approximately 40 - 50 min. The surveys of benthic habitat at each visual census were conducted in 2.1. Site Description by the line-point intercept method [21,22]. Three sea The Gulf of Aqaba (180 km long, 20 km wide) is a grass meadows sites distributed along the Jordanian coast semi-closed sea with many unique natural and physical (Figure 1) and have various types of benthic habitat features. It is geographically isolated by the narrow Strait were studied (Table 1). of Tiran. While much of the Gulf is deep (>1800 m), the northern sector has a relatively shallow shelf adjacent to 2.3. Statistical Analysis the major population centers. The Jordanian coast (27 km) All statistical analyses used to examine the data were is fringed by discontinuous belt of reefs separated by as described by [23] and implemented via StatView sandy bottoms that are usually covered by seagrass computer software. Fish abundance was described by meadows [17]. Three sites distributed along the Jorda- relative abundance (RA) and frequency of appearance nian coast (Figure 1) presenting seagrass meadows. The (FA), calculated as follows: Gulf is characterized by calm and clear water with diur- Xi nal tides in the range of less than one meter. Currents RA 100 specifically, and circulation generally, appear to be Ya largely wind-driven, with additional influence from tides, where, Xi is the pooled average abundance of species i density gradients, and evaporation [18,19]. from each depth and site, and Ya is the pooled average abundance of all species from each depth and site 2.2. Visual Census Ni All fish surveys were conducted by visual census tech- FA 100 Nt nique with SCUBA following the basic protocol outlined by [20]. In each site, three replicates of 50 m long where Ni is the number of transects in which species i marked transect lines, were deployed parallel to the sea was present and Nt is the total number of all transects. shore at two different depths; one shallow (6 m) and one Species diversity (H′) was calculated from the Shannon- deep (12 m). The replicates were laid sequentially with a Weaver Diversity Index [24]: 10 - 20 m distance separating them. In all cases, the ob- Hpi ln pi server waited about 10 min before counting to allow the fish to resume their normal behaviour. Subsequently, the where pi is the proportion of all individuals counted that were of species i. Species richness (d) was calculated 29.56 30 using Margslef’s index [25] as follows: Hotels area (HA) 29.53 (S 1) 29 d a b a q Aqaba log N A f o f Phosphate Loading l 29.5 u Berth (PLB) G 28 where S is the total number of species, N is the total 29.47 Red Sea number of individuals A B 27 34 34.5 35 A 29.44 J O R D A N 3. RESULTS Q Latitude (N) Latitude A 3.1. Abundance and Frequency of F 29.41 Tala Bay (TB) O Appearance F 29.38 L A total of 37,034 fishes were counted in the present U G study representing 132 species that belong to 35 families 29.35 0 1 2 3 4 5 km with an average of 4741.6 fish per transect. The percent 34.79 34.82 34.85 34.88 34.91 34.94 34.97 35 35.03 number of species per family showed the following rank: Longitude (E) Labridae (19.70%), Pomacentridae (8.33%), Gobiidae Figure 1. Location map of the northern tip of the Gulf of (6.06%) and Scorpaenidae, Apogonidae, Chaetodontidae, Aqaba showing fish survey transects at the three sampling sites Blenniidae and Tetraodontidae (4.55%, each). These as follows: HA = Hotels Area, PLB = Phosphate Loading Berth, eight families account for 56.82% of the total species. In TB = Tala Bay. terms of relative abundance per family the ichthyofauna Copyright © 2012 SciRes. OPEN ACCESS M. A. Khalaf et al. / Natural Science 4 (2012) 517-525 519 Table 1. Listing of study sites and abbreviations with live substrate coverage (HC = hard coral, SC = soft coral, DC and R = dead coral and rock, S = sand, SG = sea grass, others = other items which are not listed). Site HC SC DC and R S SG Others Hotels Area (HA) 1.2 0.4 2.3 24.6 71.1 0.4 Phosphate Loading Berth (PLB) 5.8 0.7 4.5 52.5 35.7 0.8 Tala Bay (TB) 3.2 3.1 7.6 15.1 69.8 1.2 showed the following rank: Lethrinidae (30.5%), Po- tralis (4.4%), C. pelloura (3.1%), and Sargocentron dia- macentridae (28.7%), Serranidae (15.4%), Siganidae dema 2.9%. These five species made up 82.8% of the (6.8%), Labridae (5.0%), Nemepteridae (2.9%) and Ca- total population. rangidae (2.6%). These 7 families account for 90.0% of The number of species (S) was significantly higher in the total population. PLB (mean S = 45.7) than in HA site (mean S = 12.8) The most abundant species (Table 2) were Neopoma- with (p = 0.0002) and TB site (mean S = 31.0) with (p = centrus miryae (23.7%), Lethrinus borbonicus (22.7%), 0.0484).