Jennifer Selgrath/Project Seahorse

Jennifer Selgrath/Project Seahorse

Using both satellite imagery and local environmental knowledge, researcher Jennifer Selgrath (@jennyselgrath) investigated how small-scale fishing has evolved over six decades on Danajon Bank, a double-barrier reef system in central Philippines.

With millions of small-scale fishers operating around the world, we need to understand the impact of these fisheries on coastal marine ecosystems. How well do marine habitats withstand and recover from overfishing and destructive fishing practices? What is the best way to track habitat destruction and recovery, and how can policy influence the fishing gears (e.g. trawl nets, traps, purse seines) that are used?

Jenny's research documents the long-term impact of small-scale fishing, as well as trade-offs between local knowledge and satellite imagery when it comes to mapping habitats and, ultimately, making policy recommendations.

(Banner photo: Project Seahorse)

Project details

Jenny’s research focuses on the Danajon Bank Ecosystem in the central Philippines.

Jenny’s research focuses on the Danajon Bank Ecosystem in the central Philippines.

The Philippines is in the coral triangle – the global center of marine biodiversity. It contains the third most extensive reef system in the world and is home to over 400 scleractinian coral species and several species of seahorses. In addition harboring rich ocean life, coral reefs in the Philippines provide food and livelihoods for many communities by supporting small-scale fisheries. Small-scale fisheries in coral reef ecosystems are characterized by the variety of fish and invertebrate species that they target and the many types of fishing gears that they use. Common fishing gears include spear fishing, various nets such as seines and gillnets, hand line fishing, and traps. Reef fisheries in the Philippines once provided abundant catches, but the reefs have become degraded and fishers now catch much less. In fact, coral reefs in the Philippines are considered to be some of the most threatened in the world due to damaging human activities, including fishing.

Changing Sustainability of Small-Scale Fisheries

For small-scale fisheries, the processes through which benign fishing becomes damaging is not well understood. Jenny interviewed hundreds of fishers to document how their fishing practices have changed over their lifetimes. She has found that small-scale fisheries have intensified over time with a growing use of gears that catch anything in their path and gears that directly damage corals and other beneficial coastal habitats, such as seagrass beds. Additionally Jenny considered if there was any evidence that changing fisheries governance influenced fishing practices. She found evidence for the ‘stickiness’ of unsustainable fishing policies; in some cases, practices adopted when governance promoted catching the maximum amount of fish over sustainability persisted decades after the policies had been revised. 

Dynamic Spatial Patterns of Small-Scale Fisheries

The sustainability of small-scale fisheries could potentially be improved by identifying locations where direct impacts and habitat damage are concentrated. Using a participatory mapping approach, Jenny worked with fishers to map where people fish and how that has changed over half a century (1960 – 2010). She has found that during that time there has been a large areal expansion of fishing grounds and a dramatic increase in fishing pressure as many more people now fishing in each location. Locations that were popular early on remained the most popular fishing spots today. This shows that there has been long-term consistency in where the fisheries and their impacts are focused.

Mapping Underwater Habitats

Detailed habitat maps are critical for conservation planning, yet for many coastal habitats only coarse-resolution maps are available. As the logistic and technological constraints of habitat mapping become increasingly tractable, habitat map comparisons are warranted. Jenny compared the accuracy and conservation implications for two approaches for mapping shallow seafloor habitats: local environmental knowledge (LEK) obtained from interviews with fishers; and remote sensing analysis of very high spatial resolution satellite imagery (2.0 m pixel size). Her work helped to identify strengths and weakness of both mapping approaches for conservation planning.  Because RS provided a more accurate estimate of habitat distributions, it would be better for conservation planning for species sensitive to fine-spatial scale seascape patterns (e.g. habitat edges), while LEK is more cost effective and appropriate for mapping coarse habitat patterns. Goals for maps used in conservation should be identified early in their development.

Spatial Resilience of Coral Reefs to Long-Term Fishing Impacts

Identifying coastal areas with a high capacity to absorb impacts from fishing without becoming degraded is one step towards effectively addressing threats to the ocean. This knowledge can be incorporated into plans for conservation actions, particularly those focusing on spatial management options such as reserves.  Jenny is currently working to identify which parts of the Danajon Bank have been able to withstand high levels of fishing impacts without becoming degraded (i.e. changing from coral dominated to algae and rubble dominated). At the locations that have a high threshold to fishing impacts, she will identify the biophysical characteristics that contribute to the location’s resilience. These findings will be incorporated into conservation planning for the region, and can help managers, scientists, and stakeholders prioritize areas for protection.

Blog posts


Images from the field


My publications 

Selgrath, J.C., Gergel, S.E., and A.C.J. Vincent. (2018). Shifting gears: Diversification, intensification, and effort increases in small-scale fisheries (1950-2010)PLoS ONE 13(3): e0190232.

Selgrath, J.C., S.E. Gergel and A.C.J. Vincent. (2017) Incorporating spatial dynamics greatly improves estimates of fishing pressure: Long-term participatory mapping of coral reef fisheries. ICES Journal of Marine Science.

Selgrath, J.C. (2017) Quantifying the development of small-scale fisheries on coral reefs, and their impact on habitats. Doctoral dissertation. The University of British Columbia, Vancouver, Canada.

Selgrath, J. C., Peterson, G. D., Thyresson, M., Nyström, M., & Gergel, S. E. (2017). Regime shifts and spatial resilience in a coral reef seascape. In Learning Landscape Ecology (pp. 301-322). Springer New York.

Selgrath, J. C., Roelfsema, C., Gergel, S. E., & Vincent, A. C. (2016). Mapping for coral reef conservation: Comparing the value of participatory and remote sensing approaches. Ecosphere, 7(5).

Selgrath, J. C., Kleiber, D., & O’Donnell, K. P. (2014) Understanding tradeoffs in fishers decision making: catch, distance, and safety influence where fishers fish.  Enhancing stewardship in small-‐scale fisheries: practices and perspectives, 36. CERMES Technical Report 73.

Ban, N. C., Caldwell, I. R., Green, T. L., Morgan, S. K., O'Donnell, K., & Selgrath, J. C. (2009). Diverse fisheries require diverse solutions. Science323(5912), 338-339.

Further reading

Allison EH, Ratner BD, Åsgård B, et al. 2012. Rights-based fisheries governance: from fishing rights to human rights. Fish Fish 13: 14–29.

Aswani S and Lauer M. 2014. Indigenous people’s detection of rapid ecological change. Conserv Biol 28: 820–8.

Ban NC, Caldwell IR, Green TL, et al. 2009. Diverse Fisheries Require Diverse Solutions. Science (80- ) 323: 338.

Cinner JE. 2010. Poverty and the use of destructive fishing gear near east African marine protected areas. Environ Conserv 36: 321–6.

Cumming GS. 2011. Spatial resilience: integrating landscape ecology, resilience, and sustainability. Landsc Ecol 26: 899–909.

Foale SJ, Adhuri D, Aliño PM, et al. 2013. Food security and the Coral Triangle Initiative. Mar Policy 38: 174–83.

Gergel SE, Stange Y, Coops NC, et al. 2007. What is the value of a good map? An example using high spatial resolution imagery to aid riparian restoration. Ecosystems: 688–702.

Gutiérrez NL, Hilborn R, and Defeo O. 2011. Leadership, social capital and incentives promote successful fisheries. Nature 470: 386–9.

Hicks CC and McClanahan TR. 2012. Assessing gear modifications needed to optimize yields in a heavily exploited, multi-species, seagrass and coral reef fishery. PLoS One 7: e36022.

Hovel KA. 2003. Habitat fragmentation in marine landscapes: relative effects of habitat cover and configuration on juvenile crab survival in California and North Carolina seagrass beds. Biol Conserv 110: 401–12.

Johnson AE, Cinner JE, Hardt MMJ, et al. 2013. Trends, current understanding and future research priorities for artisanal coral reef fisheries research. Fish Fish 14: 281–92.

Lauer M and Aswani S. 2008. Integrating indigenous ecological knowledge and multi-spectral image classification for marine habitat mapping in Oceania. Ocean Coast Manag 51: 495–504.

Liu J, Dietz T, Carpenter SR, et al. 2007. Complexity of coupled human and natural systems. Science (80- ) 317: 1513–6.

Lokrantz J, Nyström M, Norström A V., et al. 2010. Impacts of artisanal fishing on key functional groups and the potential vulnerability of coral reefs. Environ Conserv 36: 327–37.

Marcus JE, Samoilys MA, Meeuwig JJ, et al. 2007. Benthic status of near-shore fishing grounds in the central Philippines and associated seahorse densities. Mar Pollut Bull 54: 1483–94.

McClanahan TR, Graham NAJ, MacNeil MA, et al. 2011. Critical thresholds and tangible targets for ecosystem-based management of coral reef fisheries. Proc Natl Acad Sci U S A 108: 17230–3.

McClanahan TR and Mangi SC. 2004. Gear-based management of a tropical artisanal fishery based on species selectivity and capture size. Fish Manag Ecol 11: 51–60.

McClenachan LE, Ferretti F, and Baum JK. 2012. From archives to conservation: Why historical data are needed to set baselines for marine animals and ecosystems. Conserv Lett 5: 349–59.

Mumby PJ, Harborne AR, Williams J, et al. 2007. Trophic cascade facilitates coral recruitment in a marine reserve. Proc Natl Acad Sci U S A 104: 8362–7.

Olds AD, Connolly RM, Pitt KA, and Maxwell PS. 2012. Habitat connectivity improves reserve performance. Conserv Lett 5: 56–63.

Ostrom E. 2009. A general framework for analyzing sustainability of social-ecological systems. Science (80- ) 325: 419–22.

Peterson GD. 2011. Estimating Resilience Across Landscapes. Ecol Soc 6: 17–28.

Pomeroy RS, Garces LR, Pido MD, and Silvestre G. 2010. Ecosystem-based fisheries management in small-scale tropical marine fisheries: Emerging models of governance arrangements in the Philippines. Mar Policy 34: 298–308.

Reed MS. 2008. Stakeholder participation for environmental management: A literature review. Biol Conserv 141: 2417–31.

Roelfsema CM, Phinn SR, Jupiter SD, et al. 2013. Mapping coral reefs at reef to reef-system scales, 10s–1000s km2, using object-based image analysis. Int J Remote Sens 34: 6367–88.

Shepperson J, Murray LG, Cook S, et al. 2014. Methodological considerations when using local knowledge to infer spatial patterns of resource exploitation in an Irish Sea fishery. Biol Conserv 180: 214–23.

Stewart KR, Lewison RL, Dunn DC, et al. 2010. Characterizing fishing effort and spatial extent of coastal fisheries. PLoS One 5: e14451.

Thornton TF and Scheer AM. 2012. Collaborative engagement of local and traditional knowledge and science in marine environments: A review. Ecol Soc 17: 8.

Thorton DH, Branch LC, and Sunquist ME. 2011. The relative influence of habitat loss and fragmentation: Do tropical mammals meet the temperate paradigm ? Ecol Appl 21: 2324–33.

Turner SJ, Thrush SF, Hewitt JE, et al. 1999. Fishing impacts and the degradation or loss of habitat structure. Fish Manag Ecol 6: 401–20.

Vincent ACJ. 2011. Saving the shallows: focusing marine conservation where people might care. Aquat Conserv Mar Freshw Ecosyst 21: 495–9.