Species Checklist, Composition, Abundance and Distribution of Ichthyoplankton in the Sarawak Exclusive Economic Zone (EEZ) of the South China Sea with some Selected Physicochemical Water Parameters

Ainil Syamin, Alias (2021) Species Checklist, Composition, Abundance and Distribution of Ichthyoplankton in the Sarawak Exclusive Economic Zone (EEZ) of the South China Sea with some Selected Physicochemical Water Parameters. Masters thesis, Universiti Malaysia Sarawak (UNIMAS).

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Abstract

This study was conducted to obtain the ichthyoplankton composition, abundance and distribution data in the Sarawak Exclusive Economic zone (EEZ) of South China Sea by performing one time sampling at 38 stations within three different neritic zones (inner, middle and outer). Samplings were performed from 19th August to 6th October 2015 using a bongo net (0.5 m opening diameter, mesh-size of 330 μm and 500 μm) obliquely towed at speed of 2 to 3 knots, for about 20 minutes (10 minutes downward and 10 minutes upward). Each net was attached with a flow meter to measure the volume of water filtered. The physicochemical water parameters (temperature, salinity, turbidity, dissolved oxygen and pH) at surface water were measured at 38 stations, while selected physicochemical water parameters were measured only at 15 stations according to depth profile. Preserved ichthyoplankton were identified to family level and the development of fish larvae was identified (pre-flexion, flexion and post-flexion stages. The density of ichthyoplankton and Jaccard’s dissimilarity index were calculated. The one-way ANOVA and Tukey’s test was used to determine the significant difference of physicochemical water parameters among 38 stations, while Pearson correlation coefficient was used to analyse the relationship between mean values of selected 15 physicochemical water parameters according to depth profiles at three neritic zones. The influence of environmental factors on ichthyoplankton family abundance according to neritic zone was tested with Canonical Correspondence Analyses (CCA). Checklist of ichthyoplankton was prepared with general description of each family. Throughout this study, a total of 3,935 fish eggs belonging to six orders and 12 families were successfully collected, while 5,264 fish larvae with 16 order, 59 families and 40 species were obtained. The ichthyoplankton samples contained commercial family, five families of fish egg and 16 families of fish larvae. For fish larvae, 36 families are new records for Sarawak waters, while 10 families are new records for the South China Sea EEZ waters. Balistidae and Scombridae larvae were found at three different neritic zones comprising all development stages (pre-flexion, flexion and post-flexion). High abundance of fish eggs was recorded in three families namely Carangidae, Clupeidae and Scombridae (> 10%), while fish larvae had three dominant families namely Gobiidae, Engraulidae, Scombridae (> 6%). Based on neritic zone, the dominant fish larvae species was Encrasicholina punctifer (2.94 FL/100 m3) at inner neritic zone, while at middle and outer neritic zones were dominated by Tenualosa toli with 1.37 FL/100 m3 and 0.88 FL/100 m3, respectively. The highest mean density of fish egg and fish larvae were recorded at inner neritic zone with 24.57 ± 14.85 FE/100 m3 and 35.16 ± 13.58 FL/100 m3, respectively. The highest Jaccard’s dissimilarity index of fish egg was recorded between middle and outer neritic zones while the highest Jaccard’s dissimilarity index of fish larvae was recorded between inner and outer neritic zones. The range of physicochemical parameters were within the range of Malaysia Marine Water Quality Criteria and Standard (MMWQS). CCA showed that eggs of Malacostidae and Muraenidae were associated with outer neritic zone, high salinity, DO and turbidity while Labridae, Scombridae and Sphyraenidae eggs were associated at inner neritic zone with higher temperature and pH. For fish larvae, Chlorophtalmidae, Plesiopidae, Pomacentridae and Sphyraenidae were not associated with all environmental factors (neritic zone, temperature, salinity, turbidity, dissolved oxygen and pH). In conclusion, this study had shed some useful information regarding the species checklist, composition, abundance and distribution of ichthyoplankton in the Sarawak EEZ of the South China Sea that can act as baseline data for future fishery management. Keywords: Ichthyoplankton, composition, abundance, distribution, Sarawak EEZ, South China Sea

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