ICTHYOFAUNAL DIVERSITY IN CHERAI MANGROVES

       ICTHYOFAUNAL DIVERSITY IN CHERAI MANGROVES

                                                                                 AMRITHA KRISHNAN

                                                                   Natural Science

                                                                              Reg no: 233240114856

                                                                                  SNMTC, Moothakunnam

    

ABSTRACT:

Mangrove forests are crucial for coastal protection, biodiversity conservation, and providing vital ecosystem services. Mangroves provide an excellent habitat for a variety of fish. This study aims to assess the ichthyofaunal diversity of mangrove ecosystems in two different sites of the Cherai locality. Fish Samples were collected by hand handpicking, gill nets, traps, hooks, etc. The samples were collected from October 2024 to January 2025. The kind of fish species that were found in the research sites consists of 20 species that belonged to the 5 orders, 16 families, and 17 genera, of which thirteen are common to study sites

INTRODUCTION:

Mangrove is a unique and complex ecosystem because there are associations between flora and fauna closely related to local environmental factors. Mangroves are shrubs or small scrubby trees supported by prop roots. They are generally halophytes and occur in areas like estuaries and marine shorelines. Many species of mangrove plants are adapted to survive in a specific environment. Mangrove areas can be described as areas or wetland ecosystems that are very productive due to high nutrient productivity, because it obtain energy in the form of food substances brought by tidal seawater, to coastal areas and surrounding estuaries (Osland et al. 2017). Mangroves survive in salty, brackish water with various kinds of safeguard membranes that prevent salt from entering the roots and glands on the leaves that secrete salt or move it to leaves that are about to fall off. These adaptations help mangroves carve out a niche for themselves where other plants can’t grow (Jeffrey Hays, 2008). Mangroves are the most influential feature of tropical and subtropical shorelines. They show a good correlation with decreasing anthropogenic waste levels in areas where it is present. They also move carbon dioxide from the atmosphere in greater quantities than other forests. So, mangrove wetlands are considered to be great filters of the environment.

Mangroves are the most productive and natural renewable ecosystems. Mangrove habitat is a shield for marine ecosystem. Mangroves are one of the most important ecosystems in coastal area that has important role for sustainable fisheries. Characteristics of a mangrove ecosystem is the stability of structure, composition and diversity of communities. Species diversity is generally used as key parameter to describe the richness of species and its balance in community.  Ecosystem which has low diversity tend to low stability and more sensitive to external perturbations compared to high diversity.

Mangrove support rich numbers of terrestrial and aquatic species, including crustaceans, molluscs and fishes. Due to the presence of pneumatophores, prop roots and tree trunks; the places of safety for many species are available. In a mangrove, many of the species can be found to be connected directly to valuable fisheries. In other words, mangroves are said to be important for improving production in coastal fisheries. As per the ISFR 2017 report, the total mangrove area of India is 4912km sq. and it contributes 3.3% to the global mangrove cover. Nowadays mangroves are in a state of decline. Almost one-third of the world’s mangrove has been lost to coastal development over the past few years. Today, the protection of mangroves is depended almost entirely on their importance to fisheries. Mangrove habitats likely plays a variety of roles in the lives of fishes. Mangroves of south coastal region of Kerala have indigenous characteristics compared to the mangrove ecosystem of another region.

The Cherai locality in Kerala, with its blend of marine and freshwater ecosystems, represents a unique environment to study mangrove diversity and its associated fauna and flora. In the Cherai locality, the mangrove forests are an essential component of the coastal landscape. They offer a variety of ecological services such as stabilizing shorelines, filtering pollutants, and providing habitat for numerous species of birds, fish, and invertebrates. The roots of mangrove trees trap sediments and help in the accumulation of organic matter, thus creating a habitat rich in biodiversity. Moreover, these forests also act as carbon sinks, playing a crucial role in mitigating climate change by storing large amounts of carbon in their biomass and soil.

The region’s proximity to human settlements and tourism hubs presents both challenges and opportunities for biodiversity conservation. However, despite these changes, the region continues to harbor a rich and diverse biological community, particularly in the form of mangrove species and the ichthyofauna that inhabits this environment Studies focusing on the ichthyofauna and associated flora in Cherai remain limited, underscoring the need for comprehensive assessments. Furthermore, the interplay between ichthyofauna and mangrove flora in Cherai has not been thoroughly investigated.

 Ichthyofauna is a term that refers to the fish species in a specific region or body of water. Fishes are aquatic in habitat and it may be marine or fresh water. Fishes are seen in vast range of habitat like sea, ocean, lake, river, pond, estuary etc. Fishes are abundant in most bodies of water including mangrove wetlands. Mangrove provides an excellent habitat for a variety of fishes. These fishes are attracted to mangrove forests for the high availability of food, cooler water with higher oxygen content and the refuge they provide. Mangrove’s complex structure provides feeding grounds and shelter for them.

As an open ecosystem, mangroves show a higher species diversity than those areas surround it, like mudflats, seagrass beds etc. Many fish species enter the mangrove lined estuaries as post larvae and juveniles after spending the larval stage in offshore waters. Thus, mangroves are said to be unique in their function as nurseries and also support species important to the fishing industry.

Despite their importance, mangrove ecosystems are increasingly under threat from human activities such as urbanization, aquaculture, and industrial development. Pollution, climate change, and the alteration of hydrological regimes further exacerbate the decline of these valuable ecosystems. In Kerala, mangrove deforestation has been observed due to land reclamation and coastal development projects. As a result, there is a pressing need to understand the current state of mangrove ecosystems, assess their biodiversity, and identify the factors contributing to their degradation.

 

NEED AND SIGINIFICANCE

Understanding the ichthyofaunal diversity in the Cherai Mangroves is essential for conserving this critical habitat and ensuring sustainable management of its resources. As mangrove ecosystems provide vital nursery grounds and refuge for numerous fish species, documenting their diversity helps in assessing the health of the ecosystem, monitoring the impacts of human activities, and informing conservation strategies. This study not only fills a significant knowledge gap in regional marine biodiversity but also supports the development of effective policies to safeguard both the ecological balance and the livelihoods of local communities dependent on these rich natural resources.

OBJECTIVES OF THE STUDY

·        To assess the ichthyofaunal diversity in the Cherai mangroves

METHODOLOGY

For the collection of fishes two mangrove areas were chosen. Several methods can be used for collecting the fish samples from mangroves as well as other water bodies. Handpicking, gill nets, seines, cast nets, traps, harpoons, hooks and lines, spears etc. are some of the traditional techniques followed by the fishermen of Kerala. With the help of local fishermen, samples were collected from the two sites. The sample was collected seven times from October 2024 to January 2025. The fishes were collected almost early in the morning so that other disturbances in water are minimized. Rarely 2-3 times the sampling was done at night. The investigator preferred to take samples during high tide for the ease of catching fish. However, low tidal sampling was also done 2 times. Among the collected fishes, 11 were identified with the help of experts and from the previous studies on fish. The data was put together based on which mangrove site each species was observed. Then an account on species richness was done. Simpson’s diversity Index was also calculated for a comparison between the two sites.

ANALYSIS AND INTERPRETATION:

In the present study, a total of twenty species of fishes belonging to 16 families were found between the two mangrove forests. Sixteen of those species were observed at the Site A, Cherai Mangrove Forest (near the backwaters) whereas seventeen of those were from the mangroves of Site B, Cherai Beach Mangroves (near the mouth of the river): These 17 species caught from site B belongs to 14 families and the 16 species of site A belongs to 12 families.

Out of the total 20 species, thirteen were found to be common to both the sites. Four unique species could be found at the Site B, whereas only three species were unique to the Site A. Towards the last sampling times the total number of species observed were shortening. The largest number of species observed on one given day in site A and site B was 10 and 8 respectively, where the lowest number was four in site A and three in site B. It is also observed that two species (one each in a site) were observed as singulars since no other individuals of the same were found in the mangroves on the same day. Another fact observed is that many of the species captured were of juvenile forms with some exceptions of four or five. The members of family Cichlidae was found to be more in juvenile stage at both the sites. No juvenile forms of Batrachoididae, Tetraodontidae and Gobiidae families were observed during the entire study period. All the species observed in the two sites of mangroves in cherai are listed in Table 1, including the value of total number of samplings that each species was observed during collection.

Table 1

 The List of all Fishes Identified from the Two Mangrove Sites in Cherai

FISHES IDENTIFIED
FAMILY	SCIENTIFIC NAME	SITE A	SITE B
Ambassidae	Ambassis commersoni	3	2
	Ambassis dussumieri	2	4
Anabantidae	Anabas testudineus	1	0
Aplocheilidae	Aplocheilus lineatus	2	4
	Aplocheilus panchax	0	3
Batrachoididae	Colletteichthys dussumieri	1	2
Belonidae	Belone belone	3	0
Carangidae	Caranx ignobilis	2	0
Cynoglossidae	Cynoglosssus macrostomus	1	0
Cichlidae	Etroplus maculatus	2	5
	Etroplus suratensis	4	3
	Oreochromismossambicus	3	4
Eleotridae	Butis butis	2	7
Gerreidae	Gerres filamentosis	3	2
Gobiidae	Glossogobius giuris	0	3
Mugilidae	Mugil cephalus	3	2
Platycephalidae	Platycephalus indicus	2	5
Scatophagidae	Scatophagus argus	2	2
Terapontidae	Terapon jarbua	1	1
Tetraodontidae	Tetraodon fluvialitis	0	1

         

 

 

  FINDINGS AND CONCLUSION

•    A total of twenty species of fishes belonging to 16 families were found between the two mangrove forests.
•        Out of the total 20 species, thirteen were found to be common to both the sites.
•        Four unique species could be found at the Site B, whereas only three species were unique to the Site A.
•         The species unique to Site A were Anabas testudineus, Belone belone, Caranx ignobilis, Cynoglosssus macrostomus

·        The species unique to Site B were Aplocheilus panchax, Glossogobius giuris, Tetraodon fluvialitis

The study on ichthyofaunal diversity in the Cherai mangrove areas highlights the crucial role of mangrove ecosystems in supporting a rich variety of fish species. These ecosystems serve as breeding, nursery, and feeding grounds for numerous aquatic organisms, contributing to overall biodiversity and ecological balance. The findings emphasize the need for conservation efforts to protect mangroves from habitat degradation due to human activities and climate change. By understanding the intricate relationship between mangroves and fish diversity, we can promote sustainable practices that ensure the long-term health of these ecosystems. Further research and conservation initiatives will be essential to preserving the ecological integrity of the Cherai mangrove ecosystem for future generations.

REFERENCES

1. Arun Surendran,2010. Methodology for Assessing Status of Fish Stock in Mangroves. Fishery Environment.

 2. Banani Mandal, Arunava Mukherjee, Samir Banerjee, 2013. A review on the Ichthyofaunal diversity in mangrove based estuary of Sundarbans. Reviews in Fish Biology and Fisheries. 23(3), 365–374.

3. Felix, P.M., Chainho, A.G., Lima, R.F., Costa, J.L., Almeida, A.J., Domingos, I., Brito, A.C.,2015. Mangrove fish of Sao Tome Island (Gulf of Guinea): new occurrences and habitat usage. Marine and Freshwater Research. 68(1), 123-130.

4. Gupta, S.K., Gupta, P.C., 2006.General and Applied Ichthyology: Fish and Fisheries, S Chand & Company Ltd, New Delhi, pp, 11-17.

5. Hutchison, J, Spalding, M, Zu Ermgassen, P (2014) The Role of Mangroves in Fisheries Enhancement. The Nature Conservancy and Wetlands International. 54

6. Honda, K., Nakamura, Y., Nakaoka, M., Uy, W.H., Fortes, M.D.,2013. Habitat Use by Fishes in Coral Reefs, Seagrass Beds and Mangrove Habitats in the Philippines. PLoS ONE. 8(8).

7. Jeffrey Hays, 2008.Mangroves and The Plants and Animals that live there.

8. Kusuto Nanjo, Hiroyoshi Kohno, Nakamura, Y., Masahiro Horinouchi, Mitsuhiko sano, 2014. Journal of Experimental Marine Biology and Ecology. 461,216-225.

9. Laura Gajdzik, Ann Vanreusel, Nico Koedam, Jan Reubens, 2014. The mangrove forests as nursery habitats for the Ichthyofauna of Mida Creek 33 (Kenya, East Africa). Journal of the Marine Biological Association of the United Kingdom. 94(5), 865-877.

10. Liangliang Huang, Delian Huang, Zhiqiang Wu, Bin Kang, Zhongbing Chen, 2016. Temporal Variation of Fish Diversity and Assemblages and Their Associations to Environmental Variables in the Mangrove of Qinzhou Harbor, Guangxi Province, China. Turkish Journal of Fisheries and Aquatic Sciences. 16(2), 297-310.

11. Mallette, Spencer M.,2013. Comparison Study of Fish Species Richness of Two Mangrove Forests on Misali Island: Eastern (Extractive) v. Western (CORE) Mangrove Forests. Independent Study Project (ISP) Collection. 1525.

12. Mauricio Carrasquilla, Henao Francis Juanes, 2016. Mangroves enhance local fisheries catches: a global meta‐analysis. Fish and Fisheries banner. 18(1), 79-93.