scholarly journals Seasonal and Spatial Distribution Patterns of Ichthyoplankton Along the West Coast of Sri Lanka

2021 ◽  
Vol 34 (4) ◽  
Author(s):  
ALANKARAGE PUBUDINI RANAHANSIKA SILVA ◽  
◽  
RANKIRI PATHIRANNAHELAGE PRABATH KRISHANTHA JAYASINGHE ◽  
MAHADURAGE ISHARA GIMHAN RATHNASURIYA ◽  
KAHAWE PALLIYA GURUGE KSHANIKA PIYUMI GURUGE ◽  
...  
Keyword(s):  
Sri Lanka ◽  
West Coast ◽  
Larval Fish ◽  
Distribution Patterns ◽  
Demersal Fish ◽  
Southwest Monsoon ◽  
Larval Abundance ◽  
Nursery Ground ◽  
The West ◽  
Monsoon Period

Fundamental understanding of fish resources has become a crucial need in Sri Lanka for the sustainable management of fish stocks. Knowledge of ichthyoplankton essential in identifying the spawning dynamics of fish is scarce in this region of the Indian Ocean. A survey was conducted in 2018 covering different monsoon seasons to monitor the abundance, distribution, and diversity of ichthyoplankton along the west coast of Sri Lanka. Samples collected using vertical and horizontal WP2 hauls showed a total of 4095 fish eggs, with identification possible only to 3 families: Clupeidae, Engraulidae, and Cynoglossidae and 465 larval fish belonging to 23 families. The most dominant families recorded were the Siganidae, Blenniidae, Clupeidae, Gobiidae, and Engraulidae, which highlight the importance of pelagic and demersal fish along the west coast. A significant temporal pattern in egg abundance was observed with the highest abundance in March (535 10 m-3) in vertical WP2 net hauls. Furthermore, significant differences in spatial patterns of larval abundance were seen in vertical and horizontal samples. High larval fish abundances were recorded in March and during September - November, with northern regions generally having the highest abundances (~36 larvae 10 m-3). The spawning coincides with the productive southwest monsoon period (May to September). The high diversity and abundance of eggs and larvae recorded in this study indicate that the west coast is likely an important spawning and nursery ground for demersal and pelagic fish.

scholarly journals Observational Evidence of Summer Shamal Swells along the West Coast of India*

2013 ◽  
Vol 30 (2) ◽  
pp. 379-388 ◽  
Author(s):  
Johnson Glejin ◽  
V. Sanil Kumar ◽  
T. M. Balakrishnan Nair ◽  
Jai Singh ◽  
Prakash Mehra
Keyword(s):  
West Coast ◽  
Arabian Peninsula ◽  
Indian Subcontinent ◽  
Southwest Monsoon ◽  
Sea Waves ◽  
The West ◽  
Monsoon Period ◽  
West Coast Of India ◽  
Wind Sea ◽  
The Persian Gulf

Abstract Wave data collected off Ratnagiri, which is on the west coast of India, in 2010 and 2011 are used to examine the presence of the summer shamal swells. This study also aims to understand variations in wave characteristics and associated modifications in wind sea propagation at Ratnagiri. Wind data collected using an autonomous weather station (AWS), along with Advanced Scatterometer (ASCAT) and NCEP data, are used to identify the presence of summer shamal winds along the west coast of the Indian subcontinent and on the Arabian Peninsula. NCEP and ASCAT data indicate the presence of summer shamal winds over the Arabian Peninsula and northwesterly winds at Ratnagiri. This study identifies the presence of swells from the northwest that originate from the summer shamal winds in the Persian Gulf and that reach Ratnagiri during 30% of the summer shamal period. AWS data show the presence of northwest winds during May and southwest winds during the strong southwest monsoon period (June–August). Another important factor identified at Ratnagiri that is associated with the summer shamal events is the direction of wind sea waves. During the onset of the southwest monsoon (May), the sea direction is in the direction of swell propagation (northwest); however, during the southwest monsoon (June–August), a major part of the wind sea direction is from the southwest. The average occurrence of summer shamal swells is approximately 22% during the southwest monsoon period. An increase in wave height is observed during June and July at Ratnagiri due to the strong summer shamal event.

Changes in demersal fish assemblages on the west coast of South Africa, 1986–2009

2011 ◽  
Vol 33 (1) ◽  
pp. 157-170 ◽  
Author(s):  
LJ Atkinson ◽  
RW Leslie ◽  
JG Field ◽  
A Jarre
Keyword(s):  
South Africa ◽  
West Coast ◽  
Fish Assemblages ◽  
Demersal Fish ◽  
The West

Importance of wind variations and intersecting waveguides near Sri Lanka for the intraseasonal sea level variability along the west coast of India

2020 ◽  
Author(s):  
Iyyappan Suresh ◽  
Jerome Vialard ◽  
Matthieu Lengaigne ◽  
Takeshi Izumo ◽  
Muraleedharan Pillathu Moolayil
Keyword(s):  
Sri Lanka ◽  
Indian Ocean ◽  
Sea Level ◽  
Bay Of Bengal ◽  
West Coast ◽  
Equatorial Indian Ocean ◽  
Direct Connection ◽  
Local Wind ◽  
The West ◽  
Eastern Equatorial Indian Ocean

<p>Remote wind forcing plays a strong role in the Northern Indian Ocean, where oceanic anomalies can travel long distances within the coastal waveguide. Previous studies for instance emphasized that remote equatorial forcing is the main driver of the sea level and currents intraseasonal variability along the west coast of India (WCI). Until now, the main pathway for this connection between the equatorial and coastal waveguides was thought to occur in the eastern equatorial Indian Ocean, through coastal Kelvin waves that propagate around the Bay of Bengal rim and then around Sri Lanka to the WCI. Using a linear, continuously stratified ocean model, the present study demonstrates that two other mechanisms in fact dominate. First, the equatorial waveguide also intersects the coastal waveguide at the southern tip of India and Sri Lanka, creating a direct connection between the equator and WCI. Rossby waves reflected from the eastern equatorial Indian Ocean boundary indeed have a sufficiently wide meridional scale to induce a pressure signal at the Sri Lankan coast, which eventually propagates to the WCI as a coastal Kelvin wave. Second, local wind variations in the vicinity of Sri Lanka generate strong intraseasonal signals, which also propagate to the WCI along the same path. Sensitivity experiments indicate that these two new mechanisms (direct equatorial connection and local wind variations near Sri Lanka) dominate the WCI intraseasonal sea level variability, with the “classical” pathway around the Bay of Bengal only coming next. Other contributions (Bay of Bengal forcing, local WCI forcing) are much weaker.</p><p>We further show that the direct connection between the equatorial waveguide and WCI is negligible at seasonal timescale, but not at interannual timescales where it contributes to the occurrence of anoxic events. By providing an improved understanding of the mechanisms that control the WCI thermocline and oxycline variability, our results could have socio-economic implications for regional fisheries and ecosystems.</p>

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