When humans build walls and structures along coastlines, fish move in and need to find food. Scientists studied 13 different fish species living on a concrete seawall in Singapore to understand how they all manage to eat and survive together without competing too much. By analyzing what each fish species ate, researchers discovered that even though these fish eat similar foods, they’ve developed clever ways to share resources. Some fish eat more algae, while others prefer tiny creatures living in the algae. This research shows that artificial shorelines can actually support diverse fish communities when there’s enough food variety available.

The Quick Take

  • What they studied: How different fish species that eat algae-based foods manage to live together on artificial concrete seawalls without fighting over the same food sources
  • Who participated: 13 different species of fish commonly found eating algae on a granite seawall in Singapore’s urban coastal area
  • Key finding: Fish species showed different eating preferences and food sources, suggesting they’ve adapted to share available resources by specializing in different food types within the algae ecosystem
  • What it means for you: Artificial shorelines created by human development can support healthy, diverse fish communities if they have enough algae and food sources. This suggests coastal development doesn’t have to completely destroy fish habitats if designed thoughtfully.

The Research Details

Researchers collected fish samples from a concrete seawall in Singapore and used a special scientific technique called stable isotope analysis. This method works like a food fingerprint—it reveals what an animal has been eating by analyzing the chemical composition of their body tissues. The scientists compared the isotope signatures of carbon and nitrogen in each fish species to determine their diet composition. They also used computer models that combined this isotope data with information from previous studies about what these fish eat (from examining stomach contents) to create a more complete picture of each species’ diet.

The team then calculated something called ‘isotopic niche size’ for each species, which shows how varied each fish’s diet is. They also measured how much the diets of different fish species overlapped—both the typical overlap (what 40% of the fish ate) and the total overlap (what 95% of the fish ate). This two-level approach helped them understand whether fish were truly eating different things or just occasionally eating the same foods.

Understanding how fish share food is crucial for predicting whether artificial structures can support healthy fish communities. Previous research focused mainly on the physical structure of these habitats, but this study reveals that what fish eat is equally important. By studying resource partitioning—how species divide up available food—scientists can better predict which artificial habitats will support diverse fish populations and which ones might fail.

This study uses stable isotope analysis, which is a well-established scientific method considered reliable for dietary studies. The researchers strengthened their findings by combining isotope data with gut content analysis and existing literature, creating a more robust picture than any single method alone. However, the study focused on only one seawall location in Singapore, so results may not apply to all artificial shorelines worldwide. The sample size of 13 species is reasonable for this type of detailed analysis.

What the Results Show

The research revealed that the 13 fish species had distinctly different diet compositions, with some species specializing in algae while others preferred small invertebrates and microbes living within the algae. Each species showed different ‘isotopic niche sizes,’ meaning some fish had more varied diets while others were pickier eaters.

When researchers looked at how much the fish diets overlapped, they found an interesting pattern: while there was significant overlap in what the fish ‘could’ eat (the total 95% overlap), the fish actually ate differently in practice (only 40% typical overlap). This suggests the fish have evolved to specialize in different food sources even though similar foods are available to all of them.

The algal turf ecosystem proved to be incredibly rich, offering multiple food sources including actual algae, dead organic matter (detritus), bacteria and other microbes, and small invertebrates. Different fish species took advantage of different parts of this buffet, allowing many species to coexist peacefully on the same seawall.

The study found that some fish species were generalists (eating a wide variety of foods) while others were specialists (focusing on specific food types). The generalist species showed larger isotopic niche sizes, indicating they consumed more diverse diets. Interestingly, even specialist species didn’t completely avoid the foods preferred by other species, but they ate them in much smaller quantities, suggesting they had clear food preferences rather than strict dietary boundaries.

Previous research on artificial shorelines emphasized that physical structure—like the roughness and complexity of the concrete—determined which fish species could live there. This study adds an important new dimension by showing that the food available is equally critical. The findings align with ecological theory suggesting that similar species can coexist when they partition resources differently, but this is the first detailed study demonstrating this principle on artificial tropical shorelines.

The study examined fish from only one seawall in Singapore, so the results may not apply to artificial shorelines in other locations with different climates, water conditions, or algae types. The research is also a snapshot in time and doesn’t show how fish diets might change seasonally or over years. Additionally, while 13 species is a good sample for detailed analysis, there may be other fish species on this seawall that weren’t included in the study.

The Bottom Line

If you’re involved in coastal development or environmental management, this research suggests that artificial structures can support diverse fish communities if they allow algae to grow and establish. Designing seawalls with surface texture that encourages algae growth may help support fish populations. For general readers, this research indicates that human-made coastal structures aren’t necessarily ecological dead zones—they can become productive habitats with the right conditions. (Confidence level: Moderate—based on one location study)

Coastal city planners, environmental managers, and marine conservation professionals should pay attention to these findings. Aquarium hobbyists interested in understanding fish behavior may also find this relevant. This research is less directly applicable to people living inland or those not involved in coastal development decisions.

Changes in fish community composition on new artificial structures typically take months to years to establish. If new seawalls are constructed with algae-friendly designs, it may take 6-12 months for diverse fish communities to fully establish and stabilize.

Want to Apply This Research?

  • If monitoring a coastal area, track the diversity of fish species observed monthly and note algae coverage percentage. Users could photograph the seawall monthly and count visible fish species to monitor community development over time.
  • For coastal residents or environmental volunteers: participate in or support seawall monitoring programs. Document fish species sightings and algae conditions using a simple photo log. Share observations with local marine research institutions.
  • Establish a long-term visual monitoring system where the same seawall section is photographed monthly under consistent conditions. Track species diversity, algae coverage, and overall habitat health. Compare photos over seasons and years to identify trends in fish community composition.

This research describes fish ecology on artificial structures and does not provide medical or health advice for humans. The findings are based on observations from one specific location in Singapore and may not apply to all artificial shorelines worldwide. If you’re making decisions about coastal development or environmental management, consult with local marine biologists and environmental professionals who understand your specific geographic area. This article is for educational purposes and should not be used as the sole basis for environmental policy decisions.