An internship report submitted in partial fulfillment of the requirements for the degree of Master of Arts in Marine Conservation and Policy.

May, 2023

Introduction

In January of 2023, I was hired as a research intern for Mangrove Action Project (MAP) to investigate a hydrologic mangrove restoration technique called the ‘fishbone’ method, and assess whether or not the method allows for successful mangrove forest growth in the long-term. Mangrove Action Project is a U.S.-based nonprofit organization working with the U.N. Environment Programme and the Global Mangrove Alliance to restore global mangrove cover. MAP has worked on the frontlines of global mangrove restoration efforts for over a decade and is spearheading Community-Based Ecological Mangrove Restoration (CBEMR) workshops around the world to teach sustainable mangrove restoration methods.

Specifically, I was asked to collect scientific literature on the ‘fishbone’ method and to analyze both literature discussing the method as well as to collect and analyze Google Earth satellite imagery of existing fishbone sites in India over time. MAP’s goal for this project was to understand if the fishbone method succeeds or fails with restoring mangrove cover in the long-term.

Fishbone Method: Overview of the Mangrove Restoration Technique

The hydrologic ‘fishbone’ method, used as the preferred model for mangrove restoration in India today, was created by the M.S. Swaminathan Research Foundation, and is used by India’s Forest Department as the standard design for current and future mangrove restoration projects.

The fishbone method is a restoration water-canal mangrove planting technique. Fishbone mangrove restoration sites are designed as a system of water canals that look like the outline of a fish skeleton when viewed via aerial footage.

The fishbone design’s main water canal is dug at a forty-five degree angle from the natural creek (Ramasubramanian & Ravishankar, 2004). From 1999 onwards, side canals were dug thirty degrees from the one main, central canal (Ramasubramanian & Ravishankar, 2004). The side canals are designed to be parallel to one another and all attached to the main canal at 30 degree angles (Ramasubramanian & Ravishankar, 2004). Some fishbone sites have side canals coming out from both sides of the main canal, while other fishbone sites only have side canals branching out on one side of the main canal (Google Earth Pro 7.3.6.9345, 2022).

When implementing a mangrove restoration plantation “fishbone site”, the individual mangrove plants are planted on either side of the main water canal and also along both sides of the lateral side canals. “Nursery-raised mangrove saplings were planted along the trapezoid-shaped canals in the degraded areas after a buffer period of three months” (Bhakta et al., 2016). In an instruction manual made by the M.S. Swaminathan Research Foundation (MSSRF), this side canal thirty degree angle is said to reduce the rate of siltation of canals and also facilitate easy flow of tidal water (Ramasubramanian & Ravishankar, 2004).

            Canal dimensions are, “determined as per the contour levels and the tidal amplitude of the degraded area chosen for restoration” (Ramasubramanian & Ravishankar, 2004). Fishbone method canals are, “dug in a trapezoidal shape in order to plant the saplings at the mid-level of the canal. This is to ensure that the plants receive tidal water, but at the same time they are not submerged” (Ramasubramanian & Ravishankar, 2004). 

“In this technique, canals are formed so that the high saline soil gets regular tidal inundation, leaches out salts and becomes suitable for mangrove restoration” (Kathiresan, 2018).

There is a huge lack of research and understanding on how effective the fishbone method actually is and what factors necessitate the success of this method. It is not known if this technique is self-sustaining or if fishbone restoration sites require periodic dredging of fishbone canals in order to allow for the hydrologic flushing needed to support mangrove life. The fishbone method is mostly being used in India, but has started to spread to Costa Rica and abroad.

Motivation: Mangroves as a Key Component of Global Sustainability

Mangroves are tropical forests of salt-tolerant trees and shrubs with complex root systems that reside in tidal regions between the land and sea (Duke et al., 2014). Mangroves are located along estuaries and coastlines within the subtropics and tropics and have adapted to environmental conditions that very few other species can survive (Duke et al., 2014).  Mangroves are some of the most productive and complex forest systems in the world and act as vital feeding grounds and nursery habitat for thousands of species (The Ocean Portal Team, 2018), many of which are endangered (Duke et al., 2014). “Although mangroves make up less than one percent of all tropical forests worldwide, they are highly valuable ecosystems, providing an array of essential goods and services which contribute significantly to the livelihoods, well-being and security of coastal communities” (Duke et al., 2014). Mangroves provide livelihoods for hundreds of millions of people worldwide (Mangrove Action Project, 2023).

In 2014, the UN Environment Programme, “warned that the deforestation of the planet’s mangroves was exceeding average global forest loss by a rate of three to five times,” and labels mangrove habitat as, “one of the most threatened ecosystems on the planet” (Duke et al., 2014). We have already lost, “over a quarter of the earth’s original mangrove cover” (Duke et al., 2014).

Mangroves are natural “blue carbon” forests that efficiently accumulate and store large deposits of carbon from the atmosphere directly into their roots (Richards & Friess, 2016). Mangroves are efficient ways to sequester the atmospheric carbon emissions contributing to climate change and the heating and acidification of Earth’s oceans (Richards & Friess, 2016). These coastal trees also filter and purify seawater and protect our coasts from erosion and storm surge as sea levels rise (The Ocean Portal Team, 2018).

My organization, Mangrove Action Project (MAP), works through advocacy, education, and action to protect mangrove habitat for current and future generations. MAP wants to protect and restore mangrove forests because of the many vital ecosystem services that mangroves provide. Mangroves provide the marine spawning grounds vital to maintaining a balanced ocean food web, maintain biodiversity, mitigate climate change by sequestering massive amounts of carbon in their roots as well as by preventing coastal erosion through wave attenuation (Mangrove Action Project, 2023).  

The goal of my internship was to help MAP understand the spatial distribution of mangrove forests via remote sensing and to help assess current mangrove restoration techniques currently being used and how successful they are, in what conditions. “Data should be used to drive the mangrove research agenda, particularly as it pertains to monitoring of mangrove carbon stocks and the establishment of baseline local mangrove forest inventories” (Hamilton & Casey, 2016).

Objectives

MAP’s goal was to understand whether the fishbone method allows for the proper hydrologic conditions to sustain mangrove forests long-term, after many years of forest growth and build-up of decomposed leaf matter.  MAP wants to know if the reason that the Forest Department is mass-producing and implementing fishbone sites all over India is because these projects create a lot of government funding and income for the Forest Department. Most importantly, MAP seeks to understand if the fishbone method can succeed many years into the future without human intervention and periodic clearing of mangrove water channels.

For this research I first used Google Scholar to search the scientific literature for articles referencing the fishbone method in India. I then used Google Earth Pro to identify and collect satellite timeseries imagery from consecutive years of both successful, partially successful, and failed ‘fishbone’ mangrove sites along the central eastern Indian coast (Figure 1) starting in the state of Andhra Pradesh.

Figure 1. Overview Map of India’s State of Andhra Pradesh: All mangrove restoration fishbone sites are located within the red square (above) (Google Earth Pro 7.3.6.9345, 2022).

Figure 2. Overview Map of Mangrove Forest Areas of Balusuthippa Reserve Forest (Outlined in Green), Kothapalem Reserve Forest (Outlined in Blue), and Coringa Wildlife Sanctuary (Outlined in Red) (Google Earth Pro 7.3.6.9345, 2022).

Balusuthippa Reserve Forest (RF) (Figure 2) was the first mangrove forest area along Andhra Pradesh’s northeastern coast where I investigated mangrove restoration fishbone sites on Google Earth Pro. Then, I continued following Andhra Pradesh’s coastline southward, to fishbone sites within the mangroves of Kothapalem Reserve Forest (RF), directly below Balusuthippa RF. Lastly, I focused in on Coringa Wildlife Sanctuary’s mangrove fishbone sites via Google Earth Pro (Figure 2). The timeseries imagery on Google Earth Pro helped me identify changes in color and biomass of mangroves at the fishbone sites within Andhra Pradesh over time, to assess how mangrove cover and health had changed over time after initial fishbone implementation. The Indian states of Tamil Nadu and Odisha were to supposed to follow, but I did not have enough time during this internship to investigate the fishbone method in both of those regions as well. MAP needed to know the conditions in which the ‘fishbone’ method did and did not work.

Mangrove Degradation in Andhra Pradesh

Large mangrove loss within Andhra Pradesh has resulted from conversion of mangrove forest into aquaculture ponds (Ramasubramanian & Ravishankar, 2004). Aquaculture is the, “fastest growing animal-food sector in the world” (Thomas et al., 2017). Prawn farming in particular has been a large environmental stressor in Andhra Pradesh (Kathiresan, 2018).

Other reasons for mangrove degradation are more site-specific. In Andhra Pradesh, this includes clear-felling of mangrove forests for revenue generation by government agencies until 1972, causing hyper salinization of mangrove forest soil due to evaporation of water in soil and stagnation of tidal waters post-felling (Ramasubramanian & Ravishankar, 2004). Low tidal amplitude has also been an issue for mangroves in Andhra Pradesh, resulting in a deficiency of frequent tidal flushing (Kathiresan, 2018).

India’s eastern coast is vulnerable in terms of sea level rise, and after the tsunami in 2004, an increase in soil salinity along the east coast has altered floral species composition and the impacted benthic organisms in Godavari Mangrove sediment” (Kathiresan, 2018).

Kakinada Bay, which is directly north of, and connected to, the Coringa Wildlife Sanctuary Godavari Mangroves, has dealt with morphological changes and rapid siltation as well as effluent discharge with high nitrate and ammonium levels contributing to degradation (Ramasubramanian & Ravishankar, 2004) Kakinada Bay also experiences water stagnation and a lack of lateral water mixing, which is needed for diluting and clearing the pollutants out of Kakinada Bay (Ramasubramanian & Ravishankar, 2004).

Other mangrove degradation stressors in Andhra Pradesh include cyclones and floods (Kathiresan, 2018). Anthropogenic stressors other than aquaculture and prawn and shrimp farming include construction, factory discharge, pumping of municipal waste, runoff of agricultural pesticides, heavy metal accumulation in wetlands, oil pollution, felling of mangroves for firewood and basic community needs, and cattle grazing (Ramasubramanian & Ravishankar, 2004).  

Background of ‘Fishbone’ Method in Andhra Pradesh

India’s Forest Department surveyed all Godavari Estuary mangroves within the state of Andhra Pradesh to determine the degraded areas of mangrove forest within the state (Bhakta et al., 2016). “Floristic studies and vegetation surveys were undertaken in nine Reserve Forests in Godavari mangroves… using remote sensing… images. The floristic study helped in determining the nature of degraded areas and the species composition to include species for genetic composition while planting seedlings in the degraded areas” (Ramasubramanian & Ravishankar, 2004). Once degraded areas were identified, the Forest Department launched mangrove restoration projects all over the state of Andhra Pradesh, implementing a mangrove plantation canal design called ‘fishbone’ (Bhakta et al., 2016). 

“Restoration began with the digging of canals to reduce salinity, facilitate tidal flushing, and drain stagnant water using a fishbone design in order to facilitate easy inflow and outflow of tidal water. The main canals were dug at an angle of forty-five degrees to the natural creek, and the side canals were dug at an angle of thirty degrees to the main canal. The canals were dug in a trapezoidal shape in order to plant the saplings at the mid-level of the canal and to receive tidal water without submerging” (Bhakta et al., 2016).

“The restoration activity was carried out,” by groups, “trained in nursery raising and digging canals” (Ramasubramanian & Ravishankar, 2004). “Nursery-raised mangrove saplings were planted along the trapezoid-shaped canals in the degraded areas after a buffer period of three months. The eight-month-old saplings of Avicennia marina, Avicennia officinalis and Excoecaria agallocha were selected since these species tolerate a wide range of salinity and planted along the slopes of the canals (twenty to twenty-five cm from the top) with a gap of two m. Aegiceras corniculatum, Bruguiera gymnorrhiza, Rhizophora apiculata, Rhizophora mucronata and Xylocarpus moluccensis were also planted in order to ensure genetic diversity” (Bhakta et al., 2016).

Approach of ‘Fishbone’ Literature Synthesis

I approached this project by starting with a review of the scientific literature regarding the fishbone method. I analyzed nine literature sources, two of which were peer-reviewed, and planned to design a methodology to synthesize my results within a scientific literature review, but was asked by MAP to pivot away from the literature review, because it became clear that there were no voices in the scientific literature that were criticizing or critically reviewing the fishbone method. It then became my job to synthesize the fishbone method with the literature that I had reviewed.

On Google Scholar, using the peer-reviewed filter, I searched through literature with various search phrases in the hopes of finding any content discussing the fishbone method. The thirteen phrases that I used for peer-reviewed sources on Google Scholar were 1. mangrove fishbone design, 2. mangrove fish-bone design, 3. mangrove fish bone design, 4. mangrove fishbone method, 5. mangrove fish-bone method, 6. mangrove fishbone India, 7. Tamil Nadu India fishbone mangrove, 8. Orissa India fishbone mangrove, 9. Orissa India fish bone mangrove, 10. Odisha State fishbone mangrove, 11. Odisha State India fish bone mangrove, 12. fishbone channels India, 13. Tamil Nadu fishbone mangrove. I reviewed every single search result given for every search phrase.
            For grey literature, not peer-reviewed literature, I only needed to use one search phrase: “Mangrove fishbone design” on Google Scholar provided a large list of grey literature sources referencing the fishbone method.

Results of ‘Fishbone’ Literature Synthesis

Peer-reviewed literature on the topic of India’s fishbone method is scant. After using thirteen different search phrases, I found a total of only four peer-reviewed sources that briefly discussing the fishbone method. Two of the four peer-reviewed sources had content on the fishbone method, but were not available to the public without being purchased. I did not spend money accessing the third and fourth peer-reviewed sources that were inaccessible without a purchase, so I was only able to review two peer-reviewed sources for fishbone content for the duration of the internship.

I did not have any issues finding grey literature discussing the fishbone method on Google Scholar. With only one search phrase, “mangrove fishbone design”, I was immediately able to find relevant search results referencing the fishbone method within the first page of Google Scholar’s displayed results.  I didn’t need to go to the second page of results on Google Scholar, because the first page of results provided enough content.

The literature is without exception saying that the fishbone method is successful and that it is a best-practice method for the conservation and management of mangroves. With only two peer-reviewed sources and most of the grey literature, or non-peer-reviewed sources, being published by the MSSRF or by authors working with the MSSRF, I found nothing in the literature about how the fishbone method could be improved, or in which situations it was not successful. The literature all called the fishbone method a, “best practice,” conservation and management method for mangroves (Kathiresan, 2018; Ramasubramanian & Ravishankar, 2004; Bhakta et al., 2016).

After many days combing through literature that only praised the fishbone method, MAP and I realized that a practical assessment of the fishbone method would be more useful than conducting a literature review on this topic. Not enough peer-reviewed literature existed for a literature review to make sense. Also, the grey literature only applauded the method, explained how the method should be implemented, and did not critically review the fishbone method’s range of efficacy or practical usability in varied environmental conditions and locations.

There is plenty of literature explaining how to implement the fishbone method. With that, I was able to easily synthesize what it is and how to design a fishbone site. The literature lacked information about where the method works best, where it should not be used, and whether or not it requires maintenance during the many years after initial planting. I could not find information on whether the canals require dredging many years after planting. This was an important missing detail in the literature, and therefore in the fishbone synthesis that I wrote for MAP.

Approach of Investigating Timeseries Satellite Imagery of Sites

Three fishbone method mangrove restoration case studies were chosen within the Godavari River Delta of Andhra Pradesh, India. The three case studies are within the mangrove forest areas of Balusuthippa Reserve Forest (RF), Kothapalem Reserve Forest (RF), and Coringa Wildlife Sanctuary. Twenty five fishbone sites were randomly chosen while searching for sites on Google Earth Pro within the three mangrove forest areas. The criteria for the fishbone sites were for the sites to be older than 10 years and for there to be enough timeseries data on Google Earth Pro for each of the sites to be able to assess mangrove cover change over time.

Fishbone sites where the India Forest Department or MSSRF has installed fishbone canals were chosen randomly within each of the five mangrove forest areas. Percent ranges of mangrove cover that are grown and sustained for at least ten years post-plantation implementation were the variable used to define if each fishbone site is ‘successful’, ‘partially successful’, or ‘unsuccessful’.

‘Successful’ fishbone sites were defined as growing and sustaining more than seventy-five percent of mangrove cover within the confines of the fishbone site, ten or more years post-plantation implementation. ‘Partially successful’ fishbone sites were defined as growing and sustaining between thirty-five percent and seventy-five percent of mangrove cover, within the confines of the fishbone site, ten or more years post-plantation implementation. ‘Unsuccessful’ fishbone sites were defined as growing and sustaining less than thirty-five percent mangrove cover within the confines of the fishbone site, ten or more years post-plantation implementation.

When measuring the percentage of mangrove cover restored to the fishbone sites, more than ten years after initial planting, I imagined a boundary line enclosing all of the ends of each of the fishbone canals within one site. Within that imaginary boundary was the area of each fishbone site evaluated for restoration success, partial success, or unsuccess. The first timeseries image available on Google Earth Pro of each fishbone site, where the canals were dug but mangroves had not yet been planted, was used to gauge the initial mangrove cover before mangrove restoration efforts began. The latest timeseries image available on Google Earth Pro, usually taken in 2022 or 2023, depending on the fishbone site, was used to gauge the amount of mangrove cover that the site had grown and sustained over time. The change in mangrove cover between the site’s first and last timeseries images (i.e. the difference in mangrove cover between the initial timeseries image and the latest timeseries image) is what was used as the percentage of mangrove cover grown and sustained.

If more than seventy-five percent of the fishbone site area, within that imaginary boundary, that was initially barren became covered in mangrove greenery in the most recent timeseries image available on Google Earth Pro, then the fishbone site was deemed successful. If between seventy-five percent and thirty-five percent of the fishbone site area that was initially barren became covered in mangrove greenery in the most recent timeseries image available on Google Earth Pro, then the fishbone site was deemed partially successful. If less than thirty-five percent of the fishbone site area that was initially barren became covered in mangrove greenery in the most recent timeseries image available on Google Earth Pro, then the fishbone site was deemed unsuccessful.

Results of Investigating Timeseries Satellite Imagery of Sites

   Case Studies in Andhra Pradesh – Godavari River Delta

1.     Balusuthippa Reserve Forest – A Case Study

The Balusuthippa RF mangrove forest area is laden with small tributaries skirting off of the Godavari River Delta (Figure 2). Balusuthippa RF makes up a small part of the Godavari Mangroves along the northeastern coast of Andhra Pradesh (Figure 2). The Balusuthippa RF mangrove area has been affected by geomorphological water flow pattern changes within the past 150 years, caused by construction along the Gautami River (Ramasubramanian & Ravishankar, 2004).

All of the Balusuthippa RF Fishbone Sites reviewed in this study were implemented sometime between November of 2005 and August of 2009, according to satellite imagery (Google Earth Pro 7.3.6.9345, 2022). The locations of all of Balusuthippa RF’s fishbone sites are listed in Table 1 (Table 1). All fishbone sites discussed here are attached with canals to Godavari River tributaries.

Table 1. Balusuthippa RF Fishbone Site Geographic Coordinates Listed in Degrees, Minutes, Seconds (Google Earth Pro 7.3.6.9345, 2022).

Six of the nine randomly selected fishbone sites within Balusuthippa RF were partially successful. Approximately sixty-seven percent of the mangroves studied within Balusuthippa RF mangrove forest area grew and sustained somewhere between thirty-five and seventy-five percent of the site’s mangrove cover, ten or more years after plantation implementation.

Balusuthippa RF Fishbone Sites 1, 2, 3, 7, 8, and 9 were partially successful. Parts of each of the six sites regrew significant mangrove cover (Figure 3).

Figure 3. Balusuthippa RF’s Fishbone Site 1: Partially Successful Recovering Mangrove Cover (Left Image: Balusuthippa RF’s Site 1 Google Earth Pro Timeseries Image taken August, 2009; Right Image: Balusuthippa RF’s Site 1 Google Earth Pro Timeseries Image taken March, 2022) (Google Earth Pro 7.3.6.9345, 2022).

Three of the nine sites studied within Balusuthippa RF were successful. Approximately thirty-three percent of the randomly selected Balusuthippa RF fishbone sites were successful at sustaining more than seventy-five percent mangrove cover, ten or more years after plantation implementation.

Fishbone Sites 4, 5, and 6 within the Balusuthippa RF mangrove forest area were successful (Figure 4). For Sites 5 and 6, the sites were both completely surrounded by mangroves from the time of implementation until present-day, even though the actual inner areas of each of the sites were completely barren (Figure 4). Many of the other partially successful sites within the mangrove forest of Balusuthippa were not completely surrounded by mangrove cover (Figure 4). This observation may be an important factor leading to the success of Sites 5 and 6 within Balusuthippa RF, as well as other successful fishbone sites within Andhra Pradesh and greater India.

Figure 4. Balusuthippa RF’s Fishbone Site 5: Successful at Recovering Mangrove Cover (Left Image: Balusuthippa RF’s Site 5 Google Earth Pro Timeseries Image taken August, 2009; Right Image: Balusuthippa RF’s Site 5 Google Earth Pro Timeseries Image taken February, 2022) (Google Earth Pro 7.3.6.9345, 2022).

2. Kothapalem Reserve Forest – A Case Study

Kothapalem RF is a mangrove forest area laden with small tributaries skirting off of the Godavari River Delta, directly south of Balusuthippa RF (Figure 2). If not for a small tributary of the Godavari River separating Kothapalem RF and Balusuthippa RF, the two mangrove forest areas would be connected. Kothapalem RF also makes up a small part of the Godavari Mangroves along the northeastern coast of Andhra Pradesh (Figure 2). Kothapalem RF mangroves have also been affected by geomorphological water flow pattern changes within the past 150 years, caused by construction along the Gautami River (Ramasubramanian & Ravishankar, 2004).

All of the Kothapalem RF Fishbone Sites reviewed in this study were implemented sometime between December of 1985 and November of 2005, according to satellite imagery (Google Earth Pro 7.3.6.9345, 2022). However, the fishbone method was not used in Andhra Pradesh by the MSSRF and India’s Forest Department until 1986, so the sites in Kothapalem RF were implemented sometime between 1986 and November of 2005 (Kathiresan, 2018).

The locations of all of Kothapalem RF’s fishbone sites are listed in Table 2. All fishbone sites discussed here are attached with canals to Godavari River tributaries.

Table 2. Kothapalem RF Fishbone Site Geographic Coordinates in Degrees, Minutes, Seconds (Google Earth Pro 7.3.6.9345, 2022).

Nine of the thirteen randomly selected Kothapalem RF mangrove fishbone sites studied were partially successful. Approximately sixty-nine percent of the mangroves studied within Kothapalem RF grew and sustained somewhere between thirty-five and seventy-five percent of the site’s mangrove cover, ten or more years post-plantation implementation.

Kothapalem RF’s Fishbone Sites 1, 2, 3, 5, 6, 8, 10, 11, and 12 were partially successful. Parts of each of the nine partially successful sites regrew significant mangrove cover (Figure 5).

Figure 5. Kothapalem RF’s Fishbone Site 2: Partially Successful at Recovering Mangrove Cover (Left Image: Kothapalem RF’s Site 2 Google Earth Pro Timeseries Image taken November, 2005; Right Image: Kothapalem RF’s Site 2 Google Earth Pro Timeseries Image taken February, 2022) (Google Earth Pro 7.3.6.9345, 2022).

Of the thirteen sites studied within Kothapalem RF’s mangrove forest area, two of the fishbone sites were successful. Approximately fifteen-and-a-half percent of the randomly selected fishbone sites studied within Kothapalem RF were successful at sustaining more than seventy-five percent mangrove cover, ten or more years after plantation implementation.

Kothapalem RF’s fishbone sites 7 and 9 were successful (Figure 6). 

Figure 6. Kothapalem RF’s Fishbone Site 7: Successful at Recovering Mangrove Cover (Left Image: Kothapalem RF’s Site 7 Google Earth Pro Timeseries Image taken August, 2009; Right Image: Kothapalem RF’s Site 7 Google Earth Pro Timeseries Image taken February, 2022) (Google Earth Pro 7.3.6.9345, 2022).

Of the thirteen fishbone sites investigated within Kothapalem RF, two were unsuccessful (Figure 7). Approximately fifteen percent of the randomly selected fishbone sites studied at Kothapalem RF grew and sustained less than thirty-five percent mangrove cover, ten or more years after plantation implementation.

Kothapalem RF’s fishbone Sites 4 and 13 were unsuccessful (Figure 7). 

Figure 7. Kothapalem RF’s Fishbone Site 4: Unsuccessful at Recovering Mangrove Cover (Left Image: Kothapalem RF’s Site 4 Google Earth Pro Timeseries Image taken August, 2009; Right Image: Kothapalem RF’s Site 4 Google Earth Pro Timeseries Image taken February, 2022) (Google Earth Pro 7.3.6.9345, 2022).  

3. Coringa Wildlife Sanctuary – A Case Study

Coringa Wildlife Sanctuary is a protected part of the Godavari River Delta along the northeastern coast of Andhra Pradesh and makes up approximately 235 square kilometers of Godavari Mangrove forest (Figure 2). The northern borders of the sanctuary are connected to Kakinada Bay by tributaries flowing out of the bay and into the sanctuary. The southern parts of the Coringa Wildlife Sanctuary, next to Bhairavapalem, are connected to Godavari River tributaries (Figure 2).

Sites 1 and 2 within Coringa Wildlife Sanctuary are connected to tributaries off of Kakinada Bay (Figures 2, 8, & 9). Site 3 within Coringa Wildlife Sanctuary is connected to tributaries off of the Godavari River (Figure 2). The locations of all of Coringa Wildlife Sanctuary’s fishbone sites are listed in Table 3.

Table 3. Coringa Wildlife Sanctuary Fishbone Site Geographic Coordinates in Degrees, Minutes, Seconds (Google Earth Pro 7.3.6.9345, 2022).

All of the Coringa Wildlife Sanctuary fishbone sites reviewed in this study were implemented sometime between December of 1985 and March of 2002 according to satellite imagery (Google Earth Pro 7.3.6.9345, 2022). However, the fishbone method was not used in Andhra Pradesh by the MSSRF and India’s Forest Department until 1986, so the sites in Coringa Wildlife Sanctuary were implemented sometime between 1986 and March of 2002 (Kathiresan, 2018).

Of the three sites studied within Coringa Wildlife Sanctuary, all of them were successful (Figures 8 & 9). One-hundred percent of the randomly selected fishbone sites studied within the Coringa Wildlife Sanctuary were successful at sustaining more than seventy-five percent mangrove cover, ten or more years after plantation implementation.

Figure 8. Coringa Wildlife Sanctuary’s Fishbone Site 1: Successful at Recovering Mangrove Cover (Left Image: Coringa’s Site 1 Google Earth Pro Timeseries Image taken August, 2003; Right Image: Coringa’s Site 1 Google Earth Pro Timeseries Image taken February, 2022) (Google Earth Pro 7.3.6.9345, 2022).

Figure 9. Coringa Wildlife Sanctuary’s Fishbone Site 2: Successful at Recovering Mangrove Cover (Left Image: Coringa’s Site 2 Google Earth Pro Timeseries Image taken in March, 2002; Right Image: Coringa’s Site 2 Google Earth Pro Timeseries Image taken in March, 2022) (Google Earth Pro 7.3.6.9345, 2022).

Table 4. Fishbone Site Success by Forest Area within Andhra Pradesh’s Godavari River Delta: Balusuthippa Reserve Forest, Kothapalem Reserve Forest, and Coringa Wildlife Sanctuary.

            The fishbone sites studied in Balusuthippa Reserve Forest (RF) were approximately thirty-three percent successful and sixty-seven percent partially successful (Table 4). The fishbone sites studied in Kothapalem Reserve Forest (RF) were approximately fifteen-and-a-half percent successful, sixty-nine percent partially successful, and fifteen-and-a-half percent unsuccessful (Table 4). The fishbone sites studied in Coringa Wildlife Sanctuary were one-hundred percent successful (Table 4).

Balusuthippa RF and Coringa Wildlife Sanctuary tied for having the highest number of successful fishbone sites (Table 4). Both Balusuthippa and Coringa Wildlife Preserve did not have any unsuccessful fishbone sites (Table 4). Kothapalem RF had the lowest percentage of successful fishbone sites, the highest percentage of partially successful fishbone sites, and the highest percentage of unsuccessful fishbone sites out of the 3 mangrove forest areas (Table 4). Coringa Wildlife Preserve was the only mangrove forest area to have a one-hundred percent success rate, but had a much lower sample size than the other two forest areas (Table 4).

Table 5. Fishbone Site Success within the Godavari River Delta at Balusuthippa Reserve Forest, Kothapalem Reserve Forest, and Coringa Wildlife Sanctuary in Andhra Pradesh, India.

            Twenty-five total fishbone sites were studied within the Godavari River Delta of Andhra Pradesh in the areas of Balusuthippa RF, Kothapalem RF, and Coringa Wildlife Sanctuary (Table 5). Of those twenty-five fishbone sites, eight sites were successful (Table 5). Thirty-two percent of the total sites studied were successful (Table 5). Fifteen of the twenty-five total fishbone sites were partially successful (Table 5).

Discussion and Limitations

            The health of the Godavari river delta and estuary is also a big player in why these fishbone plantations are showing some success. The Godavari river delta is, “rich in sedimentation, upstream water discharge, nutrient-rich alluvial soil, in addition to the smooth topography, which increases the intertidal areas for colonization of mangroves along the east coast” (Kathiresan, 2018). Balusuthippa RF generally had good success long-term with the fishbone method.

            An interesting observation was that fishbone sites in Kothapalem RF and Balusuthippa RF that were geographically closer to the villages ended up being more successful long-term. When discussing those results with my coworkers at MAP, a colleague offered that this may be because the village worked so hard to dig the the fishbone site canals and plant the mangroves there. He believed that the communities may have a vested interest in ensuring that the mangroves that are growing at those fishbone sites near their homes are not being cut down for firewood, grazed by cattle, etc.

Coringa Wildlife Sanctuary had complete success long-term with the fishbone method. Two limitations of the Coringa Wildlife Sanctuary’s Case Study are that it has a low sample size and that the some of the sites are attached to different waterways. Differing hydrological conditions within this case study could contribute to differing results in long-term health of the fishbone sites within the sanctuary. Coringa Sites 1 and 2 are connected to the water flowing in and out of Kakinada Bay, while Coringa Site 3 is connected to tributaries with water flowing in and out of the mouth of the Godavari River.

There are twenty-eight fishbone sites within the Coringa Wildlife Sanctuary that I took coordinates down for, but didn’t have time to analyze. Future research on the success of fishbone in this area will not be difficult.

Despite the successes seen within Balusuthippa RF, Kothapalem RF, and Coringa Wildlife Sanctuary, more research needs to go into identifying the factors that caused these successes. Some examples of factors necessitating research include site-specific environmental conditions (wet, humid, and dry climates), difference in method efficacy based on mangrove forest type (deltas, lagoons, and estuaries), mangrove species, and implementation techniques (Chen & Twilley, 1999).

While three mangrove forest areas within the Godavari River Delta of Andhra Pradesh experienced some restoration success with this fishbone method, there are other regions of India that have not. Tamil Nadu and Odisha, formerly Orissa, are two states in India that have experienced significant fishbone site failures, according to some of the staff of MAP and reliable informants on the ground in India.

More research needs to go into understanding what causes differences in site success and the impacts that each factor plays on the success of the fishbone method in mangrove restoration. Without more research, we cannot determine how truly robust this fishbone method technique is, and in which situations it is successful, verses which situations it is not. Without knowing when, where, and how to use this method, as well as when, where, and how this method should not be used, huge amounts of mangrove restoration funding and conservation resources could be wasted in the future.

To get a better picture of exactly how fishbone works in site-specific conditions, it would be helpful to interview people on the ground who have seen and used the fishbone method, to see if it’s a successful method in certain circumstances. And if so, what are coordinates for these successful sites? Can those people being interviewed provide  supporting documentation on these specific successes or failures?

Other research questions that need answering are whether or not these fishbone canal systems are self-sustaining and self-flushing (maintaining themselves), or if India’s Forest Department is out dredging and clearing these canals periodically to ensure that the canals are not clogged with decomposed mangrove-leaf debris. MAP has a contact within the MSSRF that hand-dredged unsuccessful fishbone sites in Tamil Nadu with the local community. It's important to collect more information on how each of these sites are being maintained over time. Some of the sites that the MSSRF informant worked on were unsuccessful due to uncontrolled cattle grazing of the mangrove sites.

Another research question is if these fishbone plantation project managers are restoring natural hydrology and waterways around these fishbone sites.

Species selection by the Forest Department is another important factor to know about at each site that I have reviewed thus far. Which species are being planted where? The Forest Department chooses specific species, based on forest location, but it is not known which species are being used at the sites in this study, and how species type may affect the efficacy of this method.

Other research questions include who commissioned these sites and projects. It’s possible that certain organizations, e.g. India’s Forest Department, are less successful at actually implementing these sites, compared to other organizations, e.g. MSSRF. It would be useful to know who dug the canals at each site.

More than anything, it would be valuable to know if groups that are unassociated with the Forest Department or MSSRF are assessing these sites separately. I have looked for this, but have yet to find anything about this work currently being done.

I would like to continue this work investigating the fishbone method used in the Godavari District’s mangrove restoration projects and to also spend time investigating the fishbone method used in the Krishna District’s restoration projects within Andhra Pradesh to get a more broad idea of the state’s level of success with the fishbone method. The most useful information is usually gained when visiting sites in-person and asking local organizations and community members about the specific mangrove restoration sites that I am investigating.

Another factor that will effect mangrove restoration success in the future, including mangrove restoration success with the fishbone method, is how mangroves will react to climate change. “Rising temperatures and sea level due to climate change are allowing mangroves to expand their ranges farther away from the equator and encroach on temperate wetlands, like salt marshes” (The Ocean Portal Team, 2018).

In the future, I plan to continue to work for Mangrove Action Project and continue to search through scientific literature for information on factors affecting the success of the fishbone method as well as to continue to collect timeseries fishbone site imagery in the states of Tamil Nadu and Odisha in India. 

Works Cited

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Chen, R., & Twilley, R. R. (1999). Patterns of Mangrove Forest Structure and Soil Nutrient Dynamics along the Shark River Estuary, Florida. Estuaries, 22(4), 955. doi:10.2307/1353075

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Google Earth Pro 7.3.6.9345, (2022) Balusuthippa RF 16° 37' 39.2196" N, 82° 15' 40.9602" E. 2023 Maxar Technologies. [Desktop] Available at: https://www.google.com/intl/en-US/earth/versions/#earth-pro [Accessed February 2023].

Google Earth Pro 7.3.6.9345, (2022) Balusuthippa RF Site 1 Fishbone Plot 16° 38' 0.1566" N, 82° 16' 31.5726" E. Landsat / Copernicus Imagery. [Desktop] Available at: https://www.google.com/intl/en-US/earth/versions/#earth-pro [Accessed February 2023].

Google Earth Pro 7.3.6.9345, (2022) Balusuthippa RF Site 2 Fishbone 16° 37' 11.7516" N, 82° 16' 9.0222" E. 2023 Maxar Technologies. [Desktop] Available at: https://www.google.com/intl/en-US/earth/versions/#earth-pro [Accessed February 2023].

Google Earth Pro 7.3.6.9345, (2022) Balusuthippa RF Site 3 Fishbone Plot 16° 37' 5.8548" N, 82° 16' 7.0098" E. 2023 Maxar Technologies. [Desktop] Available at: https://www.google.com/intl/en-US/earth/versions/#earth-pro [Accessed February 2023].

Google Earth Pro 7.3.6.9345, (2022) Balusuthippa RF Site 4 Fishbone Plot 16° 36' 58.2768" N, 82° 16' 13.2162" E. Landsat / Copernicus Imagery. [Desktop] Available at: https://www.google.com/intl/en-US/earth/versions/#earth-pro [Accessed February 2023].

Google Earth Pro 7.3.6.9345, (2022) Balusuthippa RF Site 5 Fishbone Plot 16° 36' 46.8354" N, 82° 16' 15.6792" E. Landsat / Copernicus Imagery. [Desktop] Available at: https://www.google.com/intl/en-US/earth/versions/#earth-pro [Accessed February 2023].

Google Earth Pro 7.3.6.9345, (2022) Balusuthippa RF Site 6 Fishbone Plot 16° 36' 49.2726" N, 82° 16' 26.223" E. Landsat / Copernicus Imagery. [Desktop] Available at: https://www.google.com/intl/en-US/earth/versions/#earth-pro [Accessed February 2023].

Google Earth Pro 7.3.6.9345, (2022) Balusuthippa RF Site 7 Fishbone Plot 16° 36' 44.352" N, 82° 16' 30.3738" E. Landsat / Copernicus Imagery. [Desktop] Available at: https://www.google.com/intl/en-US/earth/versions/#earth-pro [Accessed February 2023].

Google Earth Pro 7.3.6.9345, (2022) Balusuthippa RF Site 8 Fishbone 16° 36' 35.6832" N, 82° 16' 22.71" E. Landsat / Copernicus Imagery. [Desktop] Available at: https://www.google.com/intl/en-US/earth/versions/#earth-pro [Accessed February 2023].

Google Earth Pro 7.3.6.9345, (2022) Balusuthippa RF Site 9 Fishbone Plot 16° 36' 45.0648" N, 82° 15' 52.2108" E. 2023 Maxar Technologies. [Desktop] Available at: https://www.google.com/intl/en-US/earth/versions/#earth-pro [Accessed February 2023].

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Google Earth Pro 7.3.6.9345, (2022) Coringa Wildlife Sanctuary Site 1 Fishbone Plot 16° 48' 31.68" N, 82° 15' 59.7708" E. Landsat / Copernicus Imagery. [Desktop] Available at:https://www.google.com/intl/en-US/earth/versions/#earth-pro [Accessed April 2023].

Google Earth Pro 7.3.6.9345, (2022) Coringa Wildlife Sanctuary Site 2 Fishbone Plot 16° 48' 27.1434" N, 82° 16' 18.2064" E. Landsat / Copernicus Imagery. [Desktop] Available at: https://www.google.com/intl/en-US/earth/versions/#earth-pro [Accessed April 2023].

Google Earth Pro 7.3.6.9345, (2022) Coringa Wildlife Sanctuary: Bhairavapalem Site 3 Fishbone Plot 16° 44' 41.1756" N, 82° 19' 0.2814" E. 2023 Airbus Imagery. [Desktop] Available at: https://www.google.com/intl/en-US/earth/versions/#earth-pro [Accessed April 2023].

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Google Earth Pro 7.3.6.9345, (2022) Kothapalem Site 1 Fishbone Plot 16° 35' 47.8458" N, 82° 15' 23.3208" E.  2023 Maxar Technologies. [Desktop] Available at: https://www.google.com/intl/en-US/earth/versions/#earth-pro [Accessed March 2023].

Google Earth Pro 7.3.6.9345, (2022) Kothapalem Site 2 Fishbone Plot 16° 35' 40.0842" N, 82° 15' 15.9474" E. 2023 Maxar Technologies. [Desktop] Available at: https://www.google.com/intl/en-US/earth/versions/#earth-pro [Accessed March 2023].

Google Earth Pro 7.3.6.9345, (2022) Kothapalem Site 3 Fishbone Plot 16° 35' 44.5056" N, 82° 15' 3.0996" E. 2023 Maxar Technologies. [Desktop] Available at: https://www.google.com/intl/en-US/earth/versions/#earth-pro [Accessed March 2023].

Google Earth Pro 7.3.6.9345, (2022) Kothapalem Site 4 Fishbone Plot 16° 35' 44.001" N, 82° 14' 50.1684" E. 2023 Maxar Technologies. [Desktop] Available at: https://www.google.com/intl/en-US/earth/versions/#earth-pro [Accessed March 2023].

Google Earth Pro 7.3.6.9345, (2022) Kothapalem Site 5 Fishbone Plot 16° 35' 48.3678" N, 82° 14' 52.5906" E. 2023 Maxar Technologies. [Desktop] Available at: https://www.google.com/intl/en-US/earth/versions/#earth-pro [Accessed March 2023].

Google Earth Pro 7.3.6.9345, (2022) Kothapalem Site 6 Fishbone Plot 16° 35' 58.9842" N, 82° 14' 49.7502" E.  2023 Maxar Technologies. [Desktop] Available at: https://www.google.com/intl/en-US/earth/versions/#earth-pro [Accessed March 2023].

Google Earth Pro 7.3.6.9345, (2022) Kothapalem Site 7 Fishbone Plot 16° 35' 53.4192" N, 82° 14' 41.1642" E. 2023 Maxar Technologies. [Desktop] Available at: https://www.google.com/intl/en-US/earth/versions/#earth-pro [Accessed March 2023].

Google Earth Pro 7.3.6.9345, (2022) Kothapalem Site 8 Fishbone Plot 16° 35' 53.8326" N, 82° 14' 28.6476" E. 2023 Maxar Technologies. [Desktop] Available at: https://www.google.com/intl/en-US/earth/versions/#earth-pro [Accessed March 2023].

Google Earth Pro 7.3.6.9345, (2022) Kothapalem Site 9 Fishbone Plot 16° 35' 36.1926" N, 82° 14' 28.6836" E. 2023 Maxar Technologies. [Desktop] Available at: https://www.google.com/intl/en-US/earth/versions/#earth-pro [Accessed March 2023].

Google Earth Pro 7.3.6.9345, (2022) Kothapalem Site 10 Fishbone Plot 16° 35' 29.817" N, 82° 14' 41.283" E. 2023 Maxar Technologies. [Desktop] Available at: https://www.google.com/intl/en-US/earth/versions/#earth-pro [Accessed March 2023].

Google Earth Pro 7.3.6.9345, (2022) Kothapalem Site 11 Fishbone Plot 16° 35' 29.742" N, 82° 14' 51.7452" E. 2023 Maxar Technologies. [Desktop] Available at: https://www.google.com/intl/en-US/earth/versions/#earth-pro [Accessed March 2023].

Google Earth Pro 7.3.6.9345, (2022) Kothapalem Site 12 Fishbone Plot 16° 35' 15.7056" N, 82° 14' 45.2754" E. 2023 Maxar Technologies. [Desktop] Available at: https://www.google.com/intl/en-US/earth/versions/#earth-pro [Accessed March 2023].

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