Preanal Length Research Articles

A Unique and Species-Rich Assemblage of Freshwater Glassfishes (Teleostei: Ambassidae: Dapalis) from the lower Oligocene of the Central Paratethys with the Description of Four New Species

We describe four new species of the fossil genus Dapalis (Ambassidae), Dapalis absconditus sp. nov., Dapalis octospinus sp. nov., Dapalis parvus sp. nov. and Dapalis quintus sp. nov., based on articulated skeletons with otoliths in situ from a freshwater habitat of the lower Oligocene of Raljin/Strelac (Serbia). Besides in body shape (e.g., body length, body depth, head length, preanal length), the species differ in morphological characters like, e.g., the serration of the preopercle, the length of the first two spines of the first dorsal and the anal fin and the morphology of the sagittal otoliths (e.g., ratio of otolith height to otolith length, ratio of otolith width to otolith length). Together with D. pauciserratus, also described from Raljin, these four species represent the most species-rich assemblage of freshwater Dapalis known so far. The compartmentalization of the internal structure of the spines reveals the close relationship of Dapalis and extant Ambassidae. Additionally, we discuss a new character from the ventral field of the otolith, a ventral depression, only found in species from Raljin. This new character is unique among the European Dapalis species and allows us to separate these five species into two species groups.

Sinobdella longitubulus, a new species of spiny eel (Pisces, Mastacembelidae) from the Zhu-Jiang Basin, with a note on the type locality of S. sinensis (Bleeker, 1870)

The spiny eel genus Sinobdella belongs to the family Mastacembelidae of the order Synbranchiformes. Kottelat and Lim (1994) utilised Rhynchobdella sinensis as the type species to propose the genus. Currently, it contains a single species widespread in eastern and southern China and northern Vietnam. Sinobdella longitubulus, a new species of spiny eel, is here described from the Xi-Jiang of the Zhu-Jiang Basin in Guangxi Zhuang Autonomous Region, southern China. It differs from the single congeneric species S. sinensis in having a more or less white-brown reticulated pattern on the flank, two tubular anterior nostrils longer than or equal to the rostral appendage, an anal fin heavily mottled with dark brown markings and white spots and bearing a narrow white distal margin; shorter pre-anal length; and fewer abdominal vertebrae. The validity of this new species is corroborated by its monophyly recovered in a COI gene-based phylogenetic analysis and its significant sequence divergence with S. sinensis. A note on the type locality of S. sinensis is also given; its type specimen is possibly from mountain streams of Jiangxi Province, in the lower Chang-Jiang Basin.

INTRA-SPECIFIC DIVERSITY OF THE SILVER GRUNT (Pomadasys Hasta) IN THREE LOCATIONS OF BANGLADESH BASED ON MORPHOMETRIC ANALYSIS

Morphometric variation is a useful tool for studying a species' population structure. The present study was performed to assess the intra-specific diversity between three stocks of the Silver grunt Pomadasys hasta (Khulna, Satkhira and Patuakhali of Bangladesh). Length-weight relationship, condition factor and few other morphometrics were analyzed using both univariate and multivariate approaches. A total of 105 samples were subjected to the analysis (weight (95.05 ±44.22 g) and length (16.18±2.57cm). A total of eleven morphometric traits including standard length (SL), head length (HL), pre dorsal length (Pre DL), dorsal length (DL), pre-anal length (Pre AL) , pre-pelvic length (PreVL) , pre pectoral length (PrePL), pre-orbital length (PrOL), body depth (BD), eye diameter (ED) and pre orbital length (PreOL) were measured. Significant differences were found in four morphometric measurements including head length (HL % of total length), eye diameter (ED % of HL), dorsal length (DL %) and pre dorsal length (PreDL%). A negative allometric growth was observed, as the slope b was far below 3. The highest value of b was found in Satkhira (2.7) and the lowest value of b was found in Khulna (2.07). Three separate stocks of P. hasta exhibited morphological variations in their attributes. The divergence among the stocks could have resulted from both environmental and genetic variances. The outcomes of the study will be helpful for management and conservation of natural population of Datina (P. hasta) in Bangladesh.

New species of the eel genera Dysomma and Dysommina from Vietnam, South China Sea (Anguilliformes: Synaphobranchidae).

Two new cutthroat eel species are described from Vietnam. Dysomma intermedium sp. nov. has a relatively long trunk, being about half of head length and anal-fin origin more than twice pectoral-fin length behind the pectoral-fin tip; pectoral fin well developed; dorsal-fin origin over or slightly in front of base of pectoral fin; two intermaxillary teeth; four or five compound teeth on ethmovomer; single row of seven or eight teeth on lower jaw; total lateral-line pores 70-76; and 21 pre-anal and 118-124 total vertebrae. Dysommina brevis sp. nov. differs from congeners by having a trunk shorter than head length, its length 11.1%-11.8% TL; a short pre-anal length 24.6%-25.6% TL, eye diameter 11.8%-12.3% head length; three large and one or two small teeth on ethmovomer; and fewer teeth on the upper and lower jaws. In addition, a specimen representing the first record of Dysommina orientalis in Vietnamese water is documented.

Acoustic Characteristics of Largehead Hairtail (Trichiurus japonicus) Using Multi-Frequency Detection in the Southern Sea, South Korea

This study was conducted to investigate the acoustic characteristics of largehead hairtails (Trichiurus japonicus) in the Southern Sea of South Korea from April 2022, using 18, 38, 70, 120, and 200 kHz split-beam echosounders. At two stations, juvenile (preanal length: 3.2 cm–5.8 cm) and immature (preanal length: 13.0 cm–26.0 cm) hairtails were caught by midwater trawling. Juvenile hairtails were distributed in layers without forming schools, while immature hairtails were detected as forming small, clustered schools. The mean volume backscattering strength (MVBS) of immature hairtails was more than 20 dB stronger than that of juvenile hairtails at both the 38 kHz and 120 kHz detection frequencies. Furthermore, the SV of juvenile and immature hairtails was high at 18 kHz and decreased as the frequency increased. We concluded that juvenile and immature hairtails can be distinguished according to their morphological characteristics because the distribution characteristics detected in the echograms differed according to their growth stage. Finally, these findings hold remarkable potential for applications within the field of hairtail identification. Acoustic backscatter information, as presented, offers valuable insights into age determination in this fish species.

Age, growth and length-to-weight relationship of largehead hairtail (Trichiurus lepturus) in south-eastern Australia suggest a distinct population

The age, growth rates and length to weight relationships for the south-eastern Australian population of largehead hairtail (Trichiurus lepturus) were investigated for the first time. Age was estimated by counting annuli in sectioned sagittal otoliths, with a maximum age of 8 years estimated for males and females. We found no significant differences in the growth rates of males and females over the size (12–78 cm pre-anal length (PL)) and age (0–8 years) ranges sampled. However, females in our collection were larger on average than males, and all fish sampled >60 cm PL were female, suggesting that females may grow to larger sizes than males and that sampling of greater numbers of larger and older fish may be required in future. T. lepturus growth was described by the von Bertalanffy growth function parameters L∝ = 74.89 cm PL, K = 0.13yr−1 and t0 = −0.80 yr, with the L∝ being amongst the largest reported for the species. Growth was variable, with the sizes at any given age spanning up to 50 cm PL. Female T. lepturus increased in body weight relative to length faster than males, as has been reported in other populations. The length/weight relationship for the south-eastern Australian population was significantly different, with almost no overlap, from that reported for T. lepturus in the Arabian Sea. The substantial differences in growth rates, maximum sizes and body morphometrics of T. lepturus from south-eastern Australia in comparison to other populations globally are consistent with the hypotheses that it represents a distinct population, although investigations using additional population markers are required to verify this.

Spatial Variability of Morphometric Characters of Freshwater Food Fishes from River Ganga of Districts, Kanpur, Prayagraj and Varanasi of Uttar Pradesh, India

The morphometric characters were evaluated to assess the population status of the commercial valuable food fishes collected from River Ganga at three different locations, Kanpur, Prayagraj and Varanasi. In this study, seventeen morphometric parameters were considered to examine during the month of October, 2022 to January, 2023. Usually, the various species of fishes consumed from the river Ganga. For present study, the morphometric characters like total length, fork length, standard length, pre-orbital length, post-orbital length, eye diameter, head length, pre-pectoral length, pre-dorsal length, pre-pelvic length, pre-anal length, length of dorsal fin, length of pectoral fin, length of caudal fin, length of caudal peduncle, body depth and body weight of four fish species, Labeo rohita, Rita rita, Wallago attu and Cyprinus carpio examined. A total of 25 specimens of each species were collected and the quantitative measurement of each aforesaid morphometric character provided crucial data regarding the development of fish body parts. Additionally, the positive correlations have been significantly (p < 0.01 and p < 0.05) detected amongst the selected morphometric characters of fishes. This study will be very crucial for fisheries management. Also, the findings will distribute the important standards for the geographical distribution of the commercially valuable food fishes. Further, the study defines that the growth of all fishes is suitable and the river Ganga ecosystem on three sites, Kanpur, Prayagraj and Varanasi is enormously favourable to the aquatic fauna especially fishes.

Stable isotopic and stomach content analyses reveal changes in the trophic level and feeding habit of large-head hairtail (Trichiurus lepturus) in the northern South China Sea

The feeding habit of large-head hairtail (Trichiurus lepturus) in the northern South China Sea was investigated through isotopic and stomach content analyses. The isotopic features of the hairtail at the same body size differed among regions, with the fish in coastal waters presenting higher δ15N and δ13C values compared to those in the open sea, indicating different trophic levels (TL), food habits, and isotopic baselines. According to the partial correlation of water depth with δ15N values, the sampling stations were divided into three regions based on the depth of water: coastal (20–40 m), near coastal (60–80 m), and open sea (100–200 m) regions. In the coastal region, the hairtail from stations affected by the Pearl River plume exhibited lower δ15N and δ13C values. The stomach content analysis indicated different feeding habits of the hairtail from different regions. The hairtail in the coastal and near coastal waters fed more on fish and less on crustaceans compared to the hairtail in the open sea. The relationship between δ15N and fish size exhibited two contrary patterns. First, the δ15N values increased with increasing preanal length in the hairtail sampled from the water depth of 30–40 m in section F (in fish with preanal length < 200 mm) and those samples from the water depth of 100–200 m. This finding reflected an ontogenetic shift in diet and TL. However, the δ15N values tended to decrease with the increasing preanal length of the hairtail samples collected from the water depth of 30–40 m in section F (fish with a preanal length of ~200–300 mm). These findings suggested that under the conditions of insufficient availability of high-quality prey, the larger hairtail fed more on low-TL prey to compensate for the increase energy demand, arising due to growth, which led to the observed decrease in δ15N values.

Reproduction, Early Development, and Larval Rearing of the Climbing Perch Anabas testudineus (Teleostei: Anabantidae) in Captivity

Induced spawning, early development, and larval rearing of the climbing perch Anabas testudineus were examined under captive conditions. Five female climbing perch [125.33 ± 3.27 mm SL; 70.67 ± 5.59 g BW] were paired with apparently mature males (108.50 ± 3.97 mm SL; 39.27 ± 4.70 g BW) and induced to spawn with 5,000 IU human chorionic gonadotropin (hCG) + 0.5 mL Ovaprim kg BW-1. All hCG + Ovaprim-injected fish spawned 9 – 11 h after hormone administration but saline-injected fish (control group) failed to spawn. Mean egg production per female, fertilization and hatching rates, and larval production per female were 7,667 ± 1,313, 98.11 ± 1.63, 61.01 ± 19.92, and 4,435 ± 1,041 %, respectively. Fertilized eggs (1.52 – 1.96 mm in dia) were almost spherical, non-adhesive, transparent, and buoyant due to a large, single oil globule (515 ± 33 μm in dia). First cleavage appeared 30 min post-fertilization (MPF) and egg development lasted for 20 – 24 h post-fertilization (HPF) (29°C). Newly hatched climbing perch larvae [1.73 ± 0.08 mm in total length (TL)] with yolk volume (YV) and oil globule volume (OGV) of 0.545 ± 0.104 and 0.072 ± 0.013 mm3, respectively, had no pigmented eyes or functional mouth parts and digestive tract, and immobile with the yolk sac pointed upward. Eyes became pigmented and both mouth and anus opened in 1 d old larvae (2.09 ± 0.04 mm TL) in preparation for exogenous feeding. Except for body depth (BD) and pre-anal length (PAL), a general increase in TL (1.73 – 3.72 mm), eye diameter (ED) (0.164 – 0.378 mm), head length (HL) (0.205 – 0.923 mm), and mouth gape (MG) size (0.308 – 0.552 mm) was observed, coinciding with yolk resorption in 7 d post-hatched larvae. Climbing perch larvae were reared at 4 stocking densities (25, 50, 75, 100 larvae L-1) and fed solely on live food (Brachionus rotundiformis from 2 – 12 d and Artemia nauplii from 13 – 40 d) or co-fed live food and microparticulate diet (MPD) (Artemia nauplii from 2 – 15 d and Artemia + MPD from 16 – 40 d). Mean survival rates at lower densities (25 – 50 larvae L-1) were significantly higher than those reared at 75 and 100 larvae L-1 (P &lt; 0.05). Furthermore, climbing perch larvae co-fed Artemia nauplii and MPD showed better survival (28.67 – 81.00%) than those fed solely on live food (24.88 – 64.00%). However, at the end of the 40 d trial period, growth parameters did not vary significantly among densities (P &gt; 0.05), except for the condition factor in larvae co-fed Artemia nauplii and MPD. Taken together, results demonstrate the effectiveness of hCG + Ovaprim for captive breeding and observations on the early development of climbing perch, and the feasibility of rearing the larvae at 25 – 50 L-1 on a combination of Artemia nauplii and MPD under laboratory conditions.

A new species of the conger eel genus Macrocephenchelys from deep waters of the Arabian Sea.

A new species of the genus Macrocephenchelys is described herein based on a single specimen collected from the deep-sea trawl landing at Kalamukku fish landing centre, Kerala coast, Arabian Sea. The new species is distinguished by having a dorsal-fin origin behind the middle of pectoral fin, a larger head, shorter trunk, larger gill opening, dorsal surface of body with dark-brown colour and ventral surface of head and belly with numerous patches of melanophores before anus, vertebrae 14-30-151. The new species shares most of the characteristics with Macrocephenchelys brevirostris but differs from it by having a more anterior dorsal-fin origin (vs. over the tip or slightly behind the pectoral-fin tip), larger head [15.3% total length (TL) vs. 10.5%-13.9% TL, 53.2% pre-anal length (PAL) vs. 35.8%-47.6% PAL], shorter trunk length (13.6% TL vs. 14.4%-20.6% TL, 47.3% PAL vs. 52.4%-66.2% PAL); further it shows 7.9%-8.1% genetic divergence from the sequences of M. brevirostris.

Morphometric and Meristic Diversity in Eel (Anguilla bicolor) in South Coast of Java

Indonesia is the largest exporter of eel to consumer countries such as European, America, Taiwan, Japan, South Korea, and the Middle East. Eels are catadromous fish that are in the growth phase in fresh waters and the development phase is in marine waters. Meristic measurement is done by counting the spine (vertebrates). Eel morphometric measurements include TL (Total Length), HL (Head Length), PDL (Pre-Dorsal Length), PAL (Pre-Anal Length) and ADL (Ano-Dorsal Length). The purpose of this study was to analyze the morphological, morphometric, and meristic diversity of intraspecies between populations. Based on the research, the samples identified were morphologically almost the same between the populations, this was seen from the color patterns in the form of plain black or brown and short fins. The morphometric and meristic measurements in the 3D distribution plot still appear to be clustered in one population, while in the dendrogram clade, one species is still congregated in each. The results of the interpretation of the matrix plot of the lowest diversity are the length and number of anodorsal vertebrate segments. This observation can be concluded that the TL and TV of the eel varied, while the PDL, PAL, PDV, PAV, ADV showed the intraspecies character of A. bicolor. This is because the distribution of A. bicolor eels that inhabit the waters of Java Island is widely distributed and random (panmitic).

Additional Data on Arctozenus australis Ho et Duhamel, 2019 (Pisces: Aulopiformes, Paralepididae) off Kerguelen Islands

This work clarifies the morphological data for the recently described species Arctozenus australis Ho et Duhamel, 2019. Specimens caught in the northwest of the known range of the species confirm the validity of diagnostic characters and expand the known range of the following parameters: predorsal length, prepelvic length, preanal length, distance between origins of dorsal and anal fins, head depth, distance between origins of dorsal and pelvic fins, interorbital width, caudal-peduncle depth, snout length, upper-jaw length, lower jaw, number of caudal vertebrae, preanal vertebrae, and anal fin rays.

An application of morphological analysis and DNA barcoding to identify Ipnops from the Clarion-Clipperton Zone (CCZ) as I. meadi Nielsen, 1966 with notes on other species of the genus (Aulopiformes: Ipnopidae)

Although Ipnops specimens are relatively common in the Clarion-Clipperton Fracture Zone (CCZ), an area targeted for potential future deep-sea mining, a reliable species identification has not yet been possible due to the lack of a captured specimen. In April 2012, an Ipnops specimen was caught for the first time from the eastern CCZ during an exploration cruise of the BGR. Species identification of this specimen was performed using a comparative application of morphological analysis and DNA barcoding and resulted in its clear assignment to Ipnops meadi Nielsen, 1966. Of the 23 compared morphological characters, 22 are inside the ranges available for I. meadi. Molecular analyses show a sequence distance of 0.76% divergence to an Ipnops specimen collected off Hawaii, close to the CCZ and also within the known geographical distribution range of I. meadi. The additional study of five specimens of I. meadi from the Arabian Sea has extended the previously known range of the following morphological characters of this species: gill rakers on anterior arch (17–21), head length (17.6–24.0 % SL), upper jaw length (10.7–14.0 % SL), maximum width of eye-plates (7.8–9.8 % SL), preanal length (58.8–79.0 % SL), and predorsal length (34.5–40.5 % SL). Ipnops specimens deriving from Australian waters could not be clearly assigned with confidence to one of the valid Ipnops species based on current morphological and molecular analyses. It seems possible that at least one previously undescribed Ipnops species occurs in Australian waters and further work is required on the genus to resolve uncertainties.

Pseudolaguvia meghalayaensis, a new diminutive sisorid catfish (Teleostei: Siluriformes) from Northeastern India

Pseudolaguvia meghalayaensis, a new diminutive sisorid catfish, is described from the confluence of Rongkil and Rongdal streams (tributaries of the Brahmaputra River) in Meghalaya, India. It is distinguished from its congeners by a combination of characters: striae in thoracic adhesive apparatus strongly anastomosing and break up into small rounded plaques posteromedially, smooth anterior edge of dorsal spine, 8 branched pectoral-fin rays, supraoccipital spine not reaching nuchal shield, pectoral-fin length 17.120.1% standard length (SL), predorsal length 40.443.8% SL, preanal length 71.173.1% SL, body depth at anus 15.618.1% SL, anal-fin base length 12.212.7% SL, and post adipose fin length12.312.6% SL.

A new Congrid eel, Rhynchoconger smithi sp. nov. (Anguilliformes: Congridae), from the Bay of Bengal, India

A new Conger eel species is described based on four specimens collected from Petuaghat fishing harbour, West Bengal, India. The combination of morphological characters and molecular data are discordant with the seven congeners currently recognized. Rhynchoconger smithi sp. nov. can be distinguished by having head smaller than trunk; pre-anal length more than three times in total length; a small eye, diameter 2.0-2.2 in snout length; rictus ending at a vertical through posterior margin of pupil; ethmovomerine teeth patch small, with 58-74 blunt teeth arranged in seven to eight irregular rows; vomerine teeth patch small, with 18-28 granular teeth arranged in four to six irregular rows, distinctly separated by narrow spaces from the ethmovomerine and maxillary teeth; three supraorbital pores and one supra-temporal pore; and 159+ to 164 total vertebrae. Moreover, R. smithi differs significantly from four congeners, R. nitens, R. flavus, R. ectenurus and R. gracilior, with Kimura two-parameter (K2P) distances 14.6%-20.3%.

The Length-Weight Characteristics of Five Elasmobranch Species (Pisces: Chondrichthyes) from Izmir Bay (Aegean Sea Coast of Turkey): Spring 2018

In this study, a total of 364 samples were collected and 349 of them belonged to, 349 specimens of Dasyatis pastinaca, 6 of Gymnura altavela, 5 of Torpedo marmorato, 2 of Aetomylaeus bovinus and Mustelus mustelus, were obtained by-catch in trammel nets off the Izmir Bay (Aegean sea coast of Turkey) during period of spring in 2018. Males of D. pastinaca ranged from 28–62 cm and females from 31.5-94 cm total length. The analysis of the angular coefficient (b) demonstrated that growth (in weight) in relation to length was isometric in males and females of D. pastinaca. Morphologic measurements of a total of 60 individuals to represent all individuals of the population, t test in independent groups to determine differences in males and females and all other morphometric measurements were statistically tested by multiple regression analysis (stepwise method). Therefore, difference between mean values obtained according to sexes was not found different. However, A linear correlation between weight- pelvic length for females and weight- preanal length for males according to multiple regression analysis in male and female individuals. Isometric and positive allometric growths were calculated for species of Torpedo marmorata and Gymnura altavela, respectively.

Early development of pearlside Maurolicus stehmanni off south-eastern Brazil.

The pearlside Maurolicus stehmanni is one of the most abundant mesopelagic fishes off south-eastern Brazil and plays a key role in the regional ecosystem. However, its early life history remains poorly understood. This study examined the M. stehmanni early life stages, from eggs to juveniles, including all developmental changes in external morphology. Larvae are simple in morphology and lack specialized larval structures. Notochord flexion begins at ~5.15 mm body length (BL) and larvae ≥5.95 mm BL are flexed. The relative growth of seven measured larval characters (head length, body depth, snout length, eye diameter, pre-dorsal length, pre-ventral length and pre-anal length) have transition points (allometric inflexion points), indicating biphasic growth patterns which are likely related to shifts in habitat use, feeding and behaviour. Larval development is similar to that of other Maurolicus species. The relatively fast development of the fins, photophores, swimbladder and pigmentation suggests a precocious adoption of a micronektonic lifestyle in the mesopelagic environment.

First morphometry, reproduction, and genetic data for Blennius ocellaris (Linnaeus, 1758) from the Black Sea

Two specimens of the butterfly blenny, Blennius ocellaris, were caught off the coast of Ordu (Black Sea, Turkey) in April 2021 by trammel net. The aim of this paper is to further document occurrence and distribution of the butterfly blenny for the Black Sea and for Turkish marine ichthyofauna and to provide first morphometric, reproduction, and genetic data on this species to the Black Sea fauna species. Some morphometric and meristic characters were measured and presented as the percentage of total length (TL%). All morphometric measurements except eye diameter, pre-anal length, and maximum body depth were higher in the male individual. It was observed that the head makes up almost 1/4 of the body. It was determined that the ripe eggs were in their final stage of development (Stage IV). Gonad’s weight of a female individual was 2.85 g and the number of eggs was determined as 2993. The mean egg diameter was measured as 1070.7 ±15.63 μm (from 1050.2 to 1123.1 μm). The mitochondrial DNA gene regions of 16S rRNA and COI of the specimens were sequenced and analyzed. The generated partial sequences of COI and 16S rRNA were 621 bp and 551 bp, respectively. The maximum likelihood tree generated with the COI gene sequences retrieved from the GenBank database demonstrated geographic region-based distinction and sequences of the Black Sea specimens nested with the reference specimen sequences from the Western Mediterranean Sea and the Sea of Marmara.

Rearing Silver Therapon Leiopotherapon plumbeus (Teleostei: Terapontidae) Larvae Using Euryhaline Rotifers as Starter Food

The silver therapon Leiopotherapon plumbeus is an important but dwindling freshwater food commodity in the Philippine freshwater habitats. The influence of feeding regimes on growth performance and survival of first-feeding silver therapon larvae fed euryhaline rotifers (Brachionus rotundiformis and B. plicatilis) as starter food was examined. Larvae at 2 days post-hatch (DPH) (1.93 ± 0.07 mm; 200 larvae/basin) were initially reared on rotifers for 12 days followed by Artemia nauplii from 14 to 35 DPH as follows: (A) B. rotundiformis from 2-13 DPH; (B) B. rotundiformis from 2-7 DPH and Moina micrura from 8-13 DPH; and (C) B. plicatilis from 2-13 DPH. After 35 days of rearing, mean survival rates were significantly higher in larvae fed B. rotundiformis (69.2%) than those co-fed B. rotundiformis and M. micrura (34.6%) or B. plicatilis alone (26.3%). Higher ingestion rates were observed for B. rotundiformis-fed larvae (1.6 ± 0.5 to 4.4 ± 0.5 ind larvae-1) than larvae fed B. plicatilis (0.0 to 3.2 ± 0.8 ind larvae-1) during the critical initial feeding stage. However, larvae fed B. plicatilis (20.75 ± 0.48 mm) were significantly longer than those fed B. rotundiformis alone (15.62 ± 0.40 mm) or co-fed B. rotundiformis and M. micrura (18.57 ± 0.58 mm). The fastest growth was observed in larvae fed B. plicatilis, with length increment (LI) and specific growth rate (SGR) of 18.8 mm and 6.8% day-1, respectively. Eye diameter, head length, snout length and pre-anal length increased but were not affected when larvae were fed two rotifer species. These results demonstrate that feeding euryhaline rotifer B. rotundiformis from 2 to 13 DPH followed by Artemia is a suitable feeding regime for better survival of silver therapon larvae under laboratory rearing conditions.

Effect of simulated sudden thunderstorm flood on the early stage development of Japanese flounder Paralichthys olivaceus

The early stage development response of Japanese flounder to simultaneous gradual drop in salinity (34, 24, 14 psu) and temperature with different durations (1, 3, 6 h) were investigated to gain better understanding of the decrease in natural stock and its relationship to global weather pattern changes. A series of small-scale laboratory set-up containing six replicates per treatment using plastic microplates were each stocked with 78 fertilized Japanese flounder eggs in gastrula stage and exposed to gradual salinity and temperature drop conditions followed by the recovery to ambient conditions. Two-way ANOVA showed that salinity (S) and exposure time (E) individually or as a combination (S × E) had no effects on hatching success rate, percentage of abnormality, pre-anal length, final total length at 4 days post-hatch (dph) and survival rate at 4 dph. Onset hatching time, newly hatched larvae total length and yolk sac volume showed individual effects but recorded no interaction effects between S and E. Results obtained indicated that the early developmental stages of Japanese flounder were quite resilient to the stressful conditions subjected on them.