This study focused on the annual seasonal abundance of fish larvae in the Shamlapur region. This study provides a comprehensive overview of the abundance of larval groups present in the Shamlapur area of coastal Cox's Bazar. Finally, the survival of fish larvae in the future could have a direct impact on the number of adult fish stocks.
In this large-scale study of three different regions of the Bay of Bengal, much more information about fish larvae was found. In predicting future fish populations, it is necessary to know the species composition and abundance of fish larvae and juveniles. The cumulative number of fish families and densities in the estuary decreased particularly from the lower estuary to the higher estuary, according to the distribution pattern of overall fish larvae.
The Gulf is home to some of the most extensive and unique ichthyofauna in the eastern Pacific. A more detailed analysis of ichthyoplankton species diversity, geographic distribution, species abundance, and how fish larvae are affected by changing environments has been made possible by advances in fish larval identification in the Gulf. A survey from the Bay of Bengal yielded a total of 14,584 specimens of fish larvae from 52 different families.
However, in summer, Clupeidae was the most abundant family, while Teraponidae was the least abundant.
Chapter- 3
Materials and Methods
- Study area
- Fish larvae preparation
- Morphological identification of fish larvae
- Number of larvae individual per 1000 m 3 Bongo net diameter, d = 0.50m
- Measurement of diversity
- Measurement of species richness
- Determination of the constancy of occurrence
- Statistical analysis
Fish larvae were collected from the selected location using a Bongo net (0.50 m mouth diameter, 1.3 m length and 500 µm body mesh). A flow meter (model: KC Denmark A/S) was attached to the net inlet to measure the amount of seawater filtered during each haul. The washed larvae were placed again in a beaker with fresh ethanol and each sample was placed in a petri dish one by one to be analyzed under a stereo microscope (OPTIKA Microscope ITALY C-B3) at low magnification (10x) and several images were taken.
Fish larvae were identified to family level under the stereomicroscope using the descriptions of related taxa given in Leis and Rennis (1983), Leis and Carson-Edwart (2000) and Rodriguez (2017). These measurements include total length (TL), standard length (SL), preanus length, head length, or the distance between the tip of the snout and the edge of the cleithrum, and the maximum dimension of the eye (Figure.2). . Since larval growth is allometric, the developmental stage of the larvae must be taken into account while measuring the different body areas for identification purposes.
Meristic features are countable, serially occurring structures, such as the number of myomeres, beads, or filament rays. Melanophores are pigments that are present throughout the body and define a species-specific pigmentation pattern (Rodriguez et al., 2017). Temporal variation of fish larvae was determined by the number of larvae along with diversity indices.
The diversity of the larval fish assemblage was measured by the Shannon-Wiener index (Shannon, 1949), and evenness or evenness was expressed by Pielou's evenness index (Pielou, 1966). At its most basic level, diversity refers to the number of different species that exist. The type of diversity used here is E-diversity, which is the diversity of species within a community or habitat.
Emergence sustainability was determined based on the ecological index by Schifino et al. 2004), and the following formula was used for the calculation; The spawning season was determined by considering the month before the month in which larvae began to be found at the selected station. Based on the monthly larval abundance, the spawning season of the identified families was categorized as summer, winter and rainy monsoon.
Chapter- 4 Results
- Fish larval composition and abundance
- Top three abundant families .1 Clupeidae
- Engraulidae
- Temporal density and diversity indices
- Spawning season
The percentage of constant: accessory: accidental families was 00:37:63 based on the constancy of occurrence among the 8 families (Table. 1). According to this data, only 37.5% of families use the Shamlapur area as a nursing home on a seasonal basis. It is assumed that the majority of the families (62.5%) were founded by accident due to their scarcity in this region.
Clupeidae were the most abundant larvae and contributed more than half of the total abundance (69.65%) of the Shamlapur region. This family was found in five months of a year - April, May, August, November and December (Fig. Several commercially important species under the Clupeidae family are found in Cox's Bazar and Teknaf coasts such as Tenualosa ilisha, T. toil, Hilsha kelee, Escualosa thoracata.
The species that are common under this family in this region are, Stolephorus indicus, S. Ambassidae family accounts for 5.44% of the total abundance. This family was found in three months of the sampling year - May, October and December. The average larval density was 3.75±6.88 and the highest abundance was observed in October with 17 individuals/1000 m3.
The highest density of larvae (329 individuals/1000m3) was observed in April, while no fish larvae were found in June (Figure 5). Larvae from 08 fish families were collected and their time of occurrence was used as an indication of their spawning time. Most of the families spawn in the cooler months of the year (November to February) based on the availability of their larvae (Figure.9).
Among the families, Clupeidae and Ambassidae were confirmed as spawners of summer, monsoon and winter as their larvae were found in seven months of the year (Table.1). Gerreidae, Labridae and Carangidae were confirmed as mid-winter, late summer and late winter spawners (Table Mar Apr May Jun Jul Aug Sep Oct Nov Dec Jan Feb. 9) Number of families in different spawning times (S=Summer,.
Chapter- 5 Discussion
Fish larval composition and abundance
In the Indian Ocean, Rathnasuriya et al. 2021) used morphological and genetic methods to identify 80 species belonging to 69 larval families. On the other hand, Hossain et al. 2007) reported the collection of 161 species from the Naf River estuary, which is located about 50 kilometers south of the current study site, using different types of nets. The rubber dam has created a controlled environment in the Bakkhali estuary, reducing the number of species that are the cause of this variation.
Changes in water characteristics due to a dam can significantly affect the population of species in the river. Another study conducted by Tzeng et al. 1997) at estuarine stations in Yenliao Bay confirmed Pomacentridae, Apogonidae, and Tripterygiidae as the dominant families at rocky stations, with Gobiidae being the most abundant. 2013) identified the four most common families: Sparidae, Scombridae, Clupeidae and Nemipteridae. 2012) studied Clupeidae as the most abundant, followed by Blenniidae, Teraponidae, Gobiidae, Sillaginidae, Nemipteridae and Mullidae in the Pendas River estuary in Peninsular Malaysia.
Constance of occurrence
Lower larval diversity could be associated with low productivity along Cox's Bazar-Teknaf coasts, as nutrients carried by rivers are assumed to be lost in deeper seas due to the narrow shelf (Qasim, 1977). On the other hand, Richness was highest in July and evenness was highest in January. While family richness refers to the number of different families present in a particular region, evenness refers to the number of individuals in each family present.
Pielou's equality is linked to the Shannon-Wiener index as it is determined by dividing the Shannon-Wiener index by the total number of families. In this study, the evenness index is zero (0) for June, September and December, indicating that there is no evenness. The obtained Shannon-Wiener index in this study agreed with Arshad et al. 2012) which indicated significant variation within the monsoon and intermonsoon season at the Pendas River Estuary.
The study was conducted at three different locations in the Vellar Estuary, which is located on the southeast coast of India. Fish usually undergo a planktonic phase lasting from a few weeks to a few months (Victor, 1986; Brothers et al., 1983). Studying spatial and temporal variability, as well as the availability of fish larvae in relation to environmental conditions, can provide information on the adaptation of spawning behavior and impact on the annual strength of all physical and biological processes (Somarkis et al., 2002).
Clupeidae and Ambassidae were proven in this study to be long spawners, as their larvae were recorded in all three seasons: summer, rainy monsoon and winter. Spawning of the Engraulidae family was observed in late summer, early and mid-monsoon. Although Blenniidae are known to breed in mid-winter, Mugilidae are known to do so in the early monsoon.
Gerreidae, Labridae, and Carangidae were identified as midwinter, late summer, and late winter spawners, respectively. El-Regal (2013) reported that Clupeidae and Engraulidae tended to reproduce at irregular intervals throughout the year, without a clear pattern.
Chapter- 6 Conclusion
Chapter- 7
Recommendation and Future Perspective
Larval life span in twelve families of fishes in "One Tree Lagoon", Great Barrier Reef, Australia. A study of the diversity and abundance of fish larvae in the southwestern part of the Oman Sea in 2011–2012. Abundance and diversity of reef fish larvae in Mabahiss Bay on the Egyptian Red Sea coast.
Bangladesh Coastal and Ocean Research Group, Institute of Marine and Fisheries Sciences, University of Chittagong. Temporal change in species composition and abundance of fish and decapods of a tropical seagrass bed in Cockle Bay, North Queensland, Australia. Ministry of External Affairs, Press Release: Press statement of the Honorable Foreign Minister on the decision of the arbitral tribunal/PCA.
Temporal and spatial distribution of fish and shrimp assemblage in the Bakkhali River estuary of Bangladesh in relation to some water quality parameters. Composition and diversity of Indian Ocean fish larvae using morphological and molecular methods. Distribution and abundance of fish larvae in the northern Aegean – eastern Mediterranean – in relation to early summer oceanographic conditions.
Nursery function of intertidal areas in the western Wadden Sea for group 0 sole Solea solea (L.). Seasonal and spatial distribution of fish larvae in waters over the Northwest Continental Shelf of Western Australia. Fish community structure and function in Terminos Lagoon, a tropical estuary in the southern Gulf of Mexico.
Appendix-1
Appendix-2
Appendix-3
Clupeidae larvae
Ambassidae larvae
Engraulidae larvae
Carangidae larvae
Blenniidae larvae
Mugilidae larvae
Gerreidae larvae
Labridae larvae
Brief biography of the author
