Basics of Ecosystem

Abstract

The concept and types of ecosystem are the basic pillars of the chapter along with energy flow through major types of ecosystem. The sustainability of an ecosystem is maintained if the energy flows through different tiers (viz. producer, primary consumer, secondary consumer, tertiary consumer and decomposer) in a perfect fashion. However, damage to a tier often results in the disruption of the food chain and breaks the flow of energy. The wild harvest of tiger prawn seeds in Indian Sundarban estuaries is a relevant example in this context, where huge quantum of fish juveniles (primary consumers of the ecosystem) are destroyed during tiger prawn (Penaeus monodon) seed collection and thus poses a negative impact on the demersal fish stock of the aquatic ecosystem.

Annexure 4 A: Damage to Fish Juvenile Community Due to Wild Collection of Tiger Prawn Seeds in the Indian Sundarban Estuaries

4.1.1 Introduction

The ecosystem services of estuaries are wide and intricately related to the livelihood of the surrounding population. These services include production of fishes, molluscs and crabs for commercial/economic gain of the local people, navigational channel for transportation of local people, fishing vessels and trawlers, passenger vessels, cargo ship, etc. and regulatory services like flood control, bioremediation, tidal action, etc.

The flow of water along the estuaries is hindered by thousands of nets that are laid along the stretch for trapping seeds of tiger prawn (Penaeus monodon). This profession is extremely detrimental to the ecosystem services (Roy Chowdhury and Mitra 2017). The Government of West Bengal has already banned the wild fry collection. Lack of alternative livelihoods for prawn seed collectors is one of the principle constraints on implementing any policies, laws and/or regulations geared towards the development of a sustainable resource use strategy as well as conservation effort for the wise use of the marine, coastal and estuarine resources (Ahmed et al. 2012). For this, the Government placed the enforcement of the fry collection ban into abeyance (in many developing countries) pending further review of how the resource and biodiversity could be conserved at the same time as protecting the livelihoods of 300,000 fry collectors (Williams 2002).

On this background, the present paper attempts to capture an in-depth view of the effects of prawn seed collection on the stakeholders and ecosystem services of Indian Sundarban estuaries.

4.1.2 Material and Methods

4.1.2.1 Research Site

Sundarban delta were formed by the deposited sediments from three major rivers, i.e. the Ganga, Brahmaputra and Meghna, and their dense network of smaller rivers, channels. The maximum elevation is about 10 metres above the mean sea level. The Hooghly River demarcates the western limit of Indian Sundarbans, and the eastern boundary is the Raimangal River.

We undertook this study during March to July, 2016, in and around the Patharpratima block of Indian Sundarbans region, which is situated in the southeastern part of Kakdwip subdivision. It covers 484.50 sq.km.

4.1.2.2 Data Capture

A questionnaire was developed to collect data on socio-economic condition, livelihood status and alternative ways of livelihood during the season of fry collection from the study site and its adjacent rivers. Primary data on fry collector’s activities were collected both by physical observation and interviewing with fry collectors. Secondary data and information related to the study was collected from several publications on Indian Sundarbans (Mitra et al. 1992; Mitra 1998, 2013; Mitra and Zaman 2014, 2015, 2016; Roy Chowdhury and Mitra 2017).

4.1.3 Result

• (a) Impact on socio-economic status of prawn seed collectors

• 1. Population

This study was conducted at Patharpratima block, and 210 peoples were interviewed. Total family members were 1423, which means their average family size was about 7 persons per family. Out of 1423 people, 721 were male and 702 were female (Fig. 4.4A.1). This means that ratio of male and female was 1.03:1.

Fig. 4.4A.1

Male/female ratio in the family of prawn seed collectors at Patharpratima block

• 2. Age structure

About 23% of the prawn seed collectors were children whose age ranged between 10 and 14 years. About 20.0% were in the age between 15 and 20 years. 53% were in the age group of 21–50 years and 4.0% were aging above 50 years (Fig. 4.4A.2).

Fig. 4.4A.2

Age structure of prawn seed collectors at Patharpratima block

• 3. Sex ratio

Our team made an in-depth survey in the study area and documented that 71% of the prawn seed collectors were male and 29% were female. However, in many places like Kakdwip, Lot 8, Sagar South, the profession in dominated by females (Fig. 4.4A.3).

Fig. 4.4A.3

Male/female ratio of prawn seed collectors at Patharpratima block

• 4. Religion

Both Muslim and Hindu are engaged in this profession without any conflicts. Rarely tribal communities (Bhumij, Garo, Kharria, Kol, Santhal, Oraon, Lodha–Savar, Munda, Kora, Mahilis, Malpaharias) participate in this profession.

Out of 1423 people, 1053 were Hindu, and 370 were Muslim which means 74% and 26% of the respondents in the study site were Hindu and Muslim, respectively (Fig. 4.4A.4). It is interesting to note that people of both these religions worship Bonobibi, which may be one of the reasons for religious convergence without any conflicts.

Fig. 4.4A.4

Hindu/Muslim population ratio of prawn seed collectors at Patharpratima block

• 5. Education

The data captured by our team members revealed that 83% of the children (within the age group 10–14 years) dropped out their schools in order to get ready cash. Among the remaining 17%, 12.2% passed class VIII (Junior school), and the remaining 4.8% passed class X (Secondary education) Fig. 4.4A.5.

Fig. 4.4A.5

Educational profile of prawn seed collectors at Patharpratima block

• 6. Health and diseases

The prawn seed collectors usually suffer from gastric and dermatological problems due to irregular feeding habit and continuous exposure to saline water. Many fry collectors also suffer from eye problem for screening the extremely thin tiger prawn seeds from the container containing variety of fish juveniles under the scorchy sunlight.

• (b) Impact on biodiversity spectrum

• 1. Fish juvenile loss

Due to screening of estuarine water with nets of fine mesh size, many commercially important high valued fish juveniles are also caught in the nets, but they are simply thrown away and destroyed. We observed that an average of 313 juveniles of 37 species of finfish were destroyed only for 17 tiger prawn seeds.

• 2. Uprooting of mangrove seedlings

The dragging of nets by the fry catchers along the intertidal mudflats often uproots the mangrove seedlings and saltmarsh grass (Porteresia coarctata), which otherwise may generate several ecosystem services like control of erosion, beach stabilization, bioremediation, carbon sequestration, etc.

4.1.4 Discussion

Tiger prawn seed collection is a common profession, which is detrimental to the socio-economic and biodiversity profiles of Indian Sundarbans. Apart from destruction of finfish and shell fish juveniles (Roy Chowdhury and Mitra 2017), the practice of dragging the nets along the shore uproots the mangrove seedlings. These seedlings not only control soil erosion but also act as a major sink of carbon dioxide (Agarwal et al. 2016, Mitra et al. 2016a, b, 2017; Pal et al. 2016; Zaman et al. 2016). This practice is therefore a serious threat to ecosystem services of Sundarban estuaries (Mitra and Zaman 2014, 2015, 2016). Because of recession in traditional livelihood like agriculture (due to expansion of shrimp culture activities) and lack of alternative livelihood schemes at commercial scale, people of Sundarbans are accelerating their dependency on prawn seed collection. Considering the negative impact of this profession, it is of utmost importance to procure prawn seeds from hatcheries (available in plenty from the adjacent states like Odisha and Andhra Pradesh), develop seed bank and provide alternative livelihoods through ICZM (Integrated Coastal Zone Management) programme as a separate section for this mangrove dominated World Heritage Site.

4.1.5 Conclusion

Because of salinity problem, development of tiger prawn seed hatchery could not see the light of success in and around Indian Sundarbans due to which the profession of wild collection of prawn seed has sprouted. Considering the adverse impact of this occupation on economic profile, health of the fry collectors and fish biodiversity, it is important to provide an alternative livelihood for the fry catchers. In this context Techno India University, West Bengal, has planned to develop seed bank in and around Jharkhali region to reduce the pressure on this fragile ecosystem as a whole.