La mer
Online ISSN : 2434-2882
Print ISSN : 0503-1540
Volume 57 , Issue 3-4
Showing 1-3 articles out of 3 articles from the selected issue
  • Khin Khin Gyi, Takuo OMURA, Rie NAKAMURA, Yuji TANAKA
    2019 Volume 57 Issue 3-4 Pages 73-87
    Published: 2019
    Released: May 19, 2021
    JOURNALS OPEN ACCESS
    To understand the fine-scale spatio-temporal phytoplankton dynamics with reference to the environmental properties of the water column, high-frequency samplings every 4 h, at 0.5-2 m depth intervals using a submersible pump was conducted in Tateyama Bay, Japan, for 24 h from 12 h of 12 May to 08 h of 13 May 2017. The FlowCAM, which is an automatic device, was used to identify, count and size the phytoplankton. As a result, the phytoplankton distribution significantly varied within a few meters and a short timescale(several hours)of a day. For example, Thalassiosira sp. and Prorocentrum minimum were detected at all sampling depths and times rather evenly, but the water-column total abundance of Dactyliosolen fragilissimus and Scrippsiella trochoidea significantly decreased after the 2nd set of the samplings. Speciesspecific vertical distributions were various but related to the condition(strength and depth)of the thermocline at each sampling time. These phytoplankton species-specific distributions and variations in the composition reflect the eco-physiological characteristics and size structure of phytoplankton and the short-term hydrodynamic events. The high value of chlorophyll-a in the bottom layers was not only from the phytoplankton but also from the fluorescence of the aggregate particles.
    Download PDF (2741K)
  • Nur Indah SEPTRIANI, Chinthaka Anushka HEWAVITHARANE, Bambang RETNOAJI ...
    2019 Volume 57 Issue 3-4 Pages 89-107
    Published: 2019
    Released: May 19, 2021
    JOURNALS OPEN ACCESS
    To understand the morphological changes during the silvering stages of Anguilla bicolor bicolor, 68 males and 39 females were collected from Segara Anakan in Cilacap, Central Java, Indonesia during December 2015-September 2016, May 2017 and June 2018. Specimens were categorized into 5 stages based on body and pectoral fin coloration: Y1, Y2, S1, S2 and S3. Total length of silver males ranged from 342 mm to 501 mm, with mean ± SD 414.83 ± 40.38 mm and were notably smaller than silver females which ranged from 674 mm to 937 mm(786.11± 68.98 mm). Silver females were present in catches throughout the year, with peak collection during the dry months (May and June). This corresponded to the only period when silver males were caught. Locomotion indices such as, tail, dorsal fin, anal fin, pectoral fin and eye increased with progression in silvering stages, while feeding behavior indices such as, both upper and lower jaw in males showed increasing, lower lip depth in females showed decreasing and upper lip depth in females showed decreasing and snout remained constant. The increase in locomotion indices suggested that A. bicolor bicolor from Segara Anakan underwent morphological changes in preparation for spawning migration similar to those of temperate species, but increasing upper and lower jaw in males together with all samples caught using baited traps, suggested that these tropical eels remained as feeding individuals even at late stage silver eels.
    Download PDF (1966K)
  • Shotaro TOJIMA, Izumi KINOSHITA, Yuichi HIROTA
    2019 Volume 57 Issue 3-4 Pages 109-117
    Published: 2019
    Released: May 19, 2021
    JOURNALS OPEN ACCESS
    Little is known about the early life history of critically endangered salangid, Salanx ariakensis, being one of the largest species in salangids, endemic to Ariake Bay in Japan. When surveying fish larvae and juveniles by a larva net and a beam trawl in Ariake Bay during spring tide period of December 2017, the larva net could yield a total of 10 yolk-sac, 10 preflextion, seven flextion and four postflextion larvae. No larvae occurred in any stations of rivers, and particularly the yolk-sac and preflexion larvae had been aggregated in waters around the mouth of each river. After starting the notochord flexion, they had tended to disperse westward along coasts with growth by the residual current, and to be nursed in shallow coasts with relatively polyhaline and less turbid waters for Ariake Bay. These phenomena could be found also in autumn of 2014, 2015 and 2016. Considering these information, it is likely that S. ariakensis spawn in the vicinity littorals of estuaries rather than the upper reach of rivers, as well as common salangid, Salangichthys microdon.
    Download PDF (1157K)
feedback
Top