International collaboration enabled participatory stock assessment on glass eel fisheries in West Java, Indonesia

Appropriate fishery management requires an understanding of the target species' stock dynamics. However, in the Northern Hemisphere, illegal trade and IUU (Illegal, Unreported, and Unregulated) fisheries make the assessment of recruiting glass eels extremely difficult.

On the contrary, we have successfully collected sufficient data on glass eel fisheries for detailed statistical analysis based on a community-based participatory assessment. This study was conducted by NGOs, experts, and a broad range of stakeholders from both Indonesia and East Asia.

This participatory stock assessment has contributed to eel management in Indonesia and opened up the possibility of establishing sustainable glass eel fisheries. It could also improve the data collection of glass eel fisheries worldwide.

Key Findings of the Study

• A community-based participatory assessment of glass eel fisheries was conducted by NGOs and experts in collaboration with fishermen, middlemen, eel farms, retailers, and national and local agencies.
• In 2019, more than 3,000 daily fishing practices from approximately 400 fishermen were collected in West Java, Indonesia.
• Based on this fisheries data, a sum of the abundance (10,262,840 individuals), the daily natural mortality rate, and the overall exploitation rate (25%) were estimated.Local and national agencies have disseminated
• The data collection scheme to glass eel fishermen in Indonesia.
• IUU fisheries and illegal trades have occurred in countries of the Global North. The participatory approach could potentially improve the data collection of glass eel fisheries worldwide.

1. Anguillid eels

Anguillid eels (freshwater eels) are among the most commercially important freshwater fish species worldwide, and glass eels have been intensively captured for aquaculture. Although caught and traded worldwide, East Asia is the center of demand for aquaculture and consumption.

Following the decline of the A. japonica (Japanese eel) glass eel catch and the EU A. anguilla (European eel) trade ban in 2010, other regions, such as Southeast Asia, have become increasingly important sources of juvenile Anguilla spp., for both Southeast and East Asian farms. Recent customs trade data have shown substantial shifts in trade patterns related to live eels, especially juveniles.

This trade has sometimes shifted to species/populations in Southeast Asia, where little fisheries management exists to ensure a legal and sustainable harvest.

There are currently 19 species/subspecies of freshwater eels in the genus Anguilla. All anguillids are catadromous, spawning in offshore oceanic waters, and their leaf-like leptocephalus larvae migrate to freshwater and estuarine habitats after metamorphosing into 'glass eels'.

They spend various numbers of years in continental waters as 'yellow eels' for most of their life until the onset of sexual maturation. Then, they migrate out of freshwater or estuaries toward their spawning areas in the open ocean as 'silver eels'.

2. Indonesian Shortfin Eel Conservation Project

The Indonesian Shortfin Eel, A. bicolor bicolor, is farmed and processed in Indonesia and exported to Japan. With the rising demand for tropical eels, the "Indonesian Shortfin Eel Conservation Project" was launched in 2018 by AEON, one of the largest Japanese retailers, in association with PT. Iroha Sidat Indonesia (IROHA), a supplier of the Indonesian Shortfin Eel, along with WWF Indonesia, WWF Japan, and eel experts.

This project aimed to improve the glass eel fishery in West Java based on the MSC Fisheries Standard and eel farming operated by IROHA based on the existing ASC Standards for sustainable utilization of eels. Thus, the Fishery Improvement Project (FIP) and Aquaculture Improvement Project (AIP) were launched as the first FIP/AIP projects for anguillid eels worldwide.

Data collection from the glass eel fishery was an important aspect of the action plan for the FIP, aiming to estimate the stock status of the eels and the species composition of the catches. The project team worked on developing a data collection scheme that is high-resolution enough for statistical analysis and management measures.

3. Aims of this study

Appropriate fishery management requires an understanding of the target species' stock dynamics. Fisheries-independent scientific monitoring can provide high-quality data; however, such monitoring is often financially and technically challenging, particularly in the Global South, where stock assessment often relies on fishery data. This situation is more challenging for small-scale fisheries, where catch information is not readily available and collecting reliable fisheries data can be difficult.

In Indonesia, glass eel fisheries are small-scale operations conducted independently by many individuals, making data collection challenging. Therefore, this study aimed to test whether community-based participatory stock assessments could contribute to managing glass eel fisheries.

4. Research Content

The study was conducted in the Cimandiri River Estuary, West Java, Indonesia, where IROHA primarily sourced its aquaculture seed. As this was the first step in developing an assessment scheme, fishery data were collected as the gross catch of glass eels (i.e., not species-specific).

To develop a community-based participatory monitoring scheme for glass eel fisheries, discussions were facilitated among relevant stakeholders (fishermen, middlemen, local and national fishery agencies, NGOs, and experts). From August 2016 to December 2023, more than 30 meetings were held.

The research team contacted one large middleman, 12 small middlemen, and approximately 400 fishermen, all of whom agreed to participate in the data collection scheme. With all middlemen agreeing to data collection, it can be assumed that almost 100% of fishermen in the study area voluntarily collected fishery data. The research team collected data on 3,351 daily fishing practices in the Cimandiri River from 1 January to 9 December 2019.

The glass eel fishery data collected in 2019 were sufficient enough to be analyzed using a generalized depletion model. The total sum of the abundance estimates was 10,262,840 individuals, which led to an overall exploitation rate of 24.9 % for glass eel fisheries. The estimated daily natural mortality rate was 0.011 day^-1.

5. Outcomes of the Study and Future Directions

The data collection scheme for glass eel fisheries, developed through this participatory research, has been disseminated by local and national agencies to glass eel fishermen in Indonesia and has contributed to facilitating data collection for glass eel fisheries in the country.

Illegal trade and IUU (Illegal, Unreported, and Unregulated) fisheries occur with glass eels worldwide, especially in temperate species such as the American, European, and Japanese eels. This situation makes data collection for glass eel fisheries extremely difficult. However, this study successfully collected glass eel fishery data, based on which we were able to estimate recruitment, natural mortality, and exploitation rates.

This community-based participatory stock assessment has contributed to eel management in Indonesia and could improve data collection for glass eel fisheries worldwide.

In the future, this data collection framework can be improved in the following ways. First, a longer coverage time is required—in this study, only one year was included. The second point is the need for better species resolution. In this study, taxon resolution was limited to the genus. Previous studies have reported three anguillid eel species in the Cimandiri River: A. bicolor bicolor, A. marmorata, and A. bengalensis.

The data collection scheme should be species-specific, conducting scientific research along with participatory data collection to determine the species composition of glass eels caught by fishermen.

Additionally, for the conservation and sustainable use of anguillid eel species in Indonesia, fisheries data should be collected for glass eels and other life stages, such as yellow and silver eels, to develop a feasible management plan. Furthermore, integrating stakeholders, not only for data collection but also for decision-making, can help improve fishery management.

The paper is published in the journal Marine Policy.

More information:
Ronny Irawan Wahju et al, Participatory stock assessment in West Java contributes to the management of glass eel fisheries in Indonesia, Marine Policy (2024). DOI: 10.1016/j.marpol.2024.106103

Provided by Chuo University