you're reading...

Coastal Management

Local natural resource management can combat the effects of global environmental disturbances

Paper: McClanahan, T.R.; Abunge, C.A. Catch rates and income are associated with fisheries management restrictions and not an environmental disturbance, in a heavily exploited tropical fishery. Marine Ecology Progress Series 513: 201-210, 2014. doi: 10.3354/meps10925

 A picture is worth a thousand words

Schutte 12.29

In southern Kenya, fishing restrictions had a greater positive impact on fisheries than did the negative effects of an increased sea surface temperature event.

Why we care

The scope of environmental problems can be daunting and sometimes hearing scientific news can be depressing. Corals are bleaching, climate change is threatening crop and water supplies, and fish stocks are projected to decrease in the future. However, it’s important to remember that without the sometimes depressing information, we can’t work towards effective solutions to these problems. And solutions do exist! For example, a northern state in Germany last year met 120% of their energy needs using renewable energy. We can combat climate change and other seemingly insurmountable problems!

This paper compares the influence of fishing pressure and environmental disturbance (increasing water temperatures, in this case) on coastal fisheries catches in Kenya. We actually know very little about the impacts of tropical fisheries management, despite the fact that demand for these resources is increasing while human and environmental impacts are becoming more severe.


The authors examined data on water temperatures, abundance of corals and other stationary reef organisms, and the number of fish caught over time, until 2011, along the southern coast of Kenya. The 1997 – 1998 El Niño event caused widespread increased ocean temperatures that altered stationary organism composition and abundance on the seafloor, coincident with fisheries closures and data collection.

Stationary organism and fisheries catch data was available starting in 1995 or 1996 for seven sites along the coast of Kenya and starting in 2001 – 2009 in nine additional sites. Stationary organism data was pooled into calcifying organism (like coral) percent cover and non-calcifying (like algae) percent cover, since these two groups of organisms may differentially affect fish abundances. Fish abundances were quantified using fish weights. Fish prices were combined with abundances to compute fishing revenues for analysis. Only seafloor-associated fish that fed in coastal environments were included in analyses.

Analyses were intended to compare the influence of sea temperatures, seafloor cover, and management strategies (divided into five groups based on management style and intensity) on fish catches. The authors used economic models commonly used to test for relationships between a set of variables and product prices. Analyses were able to specifically test whether temperatures or the two classes of reef organisms affected fish catches more than fisheries management did. The authors also tested for statistical trends in fish catches to determine whether the composition of catches changed over time.



The relationship between the number of fishermen on the water and their average catch. Arrows show the direction of time. After fisheries restrictions were implemented in the early 2000’s, the catch per fisherman increased even when there were as many fisherman on the water as in previous years.

Sea surface temperatures were not statistically linked to fish catches. Seafloor coverage by calcifying and non-calcifying organisms was correlated with catch rates, but cover changes did not precede catch rates and so there was no support for the hypothesis that cover changes influenced catch rates. Increased sea surface temperatures associated with the El Niño event, however, did cause changes in seafloor coverage.

After the El Niño event, catch rates and fisheries income increased as a result of fishing gear restrictions. Fish sizes for the most commonly caught species also rose during the study period. Revenue increases could be an artifact of a shift in the composition of fish catches, but statistical analyses indicated that this was not the case.

Scientists have thought for some time that reductions in seafloor coverage by reef corals and other calcifying organisms affect reef fish abundance and composition, but that these trends are difficult to detect because there is a lag time of five or ten years before these changes occur. This dataset covers more than ten years and does not support this hypothesis, although the authors cite other studies that do support it.


Revenue per fisherman increased throughout the study period. Interestingly, the authors do not address why beach seine areas (considered “negative management controls”) and sites with no restrictions saw an increase in revenue per fisherman as well. Perhaps it’s a spillover effect from increased fish stocks in nearby restriction areas?

The authors credit this difference in outcome to the specific characteristics of Kenyan fisheries. Large-bodied predators at the top of the food chain have largely been fished out of these waters, perhaps leaving behind more disturbance-tolerant species which are also profitable when caught. The species that are caught in Kenyan coastal fisheries may also be less dependent on coastal reefs with nearby seagrass and sandy habitats providing alternative food sources. Finally, it is possible that the El Niño event caused a less intense and shorter-lasting disturbance on Kenyan coral reefs than elsewhere in the world, which may have impacted fisheries elsewhere more severely.

Nevertheless, the authors stress that at least in Kenya’s case, the impact of fisheries management cannot be overlooked. Fish catches and fisherman revenues responded positively over time to management-induced restrictions more than they responded negatively to one of the most impactful climate events in recent history. This suggests that in the face of globally-caused environmental problems with significant consequences, properly implemented local measures can positively influence natural resource supplies. There is hope.


No comments yet.

Post a Comment


  • by oceanbites 2 months ago
    Happy Earth Day! Take some time today to do something for the planet and appreciate the ocean, which covers 71% of the Earth’s surface.  #EarthDay   #OceanAppreciation   #Oceanbites   #CoastalVibes   #CoastalRI 
  • by oceanbites 3 months ago
    Not all outdoor science is fieldwork. Some of the best days in the lab can be setting up experiments, especially when you get to do it outdoors. It’s an exciting mix of problem solving, precision, preparation, and teamwork. Here is
  • by oceanbites 4 months ago
    Being on a research cruise is a unique experience with the open water, 12-hour working shifts, and close quarters, but there are some familiar practices too. Here Diana is filtering seawater to gather chlorophyll for analysis, the same process on
  • by oceanbites 5 months ago
    This week for  #WriterWednesday  on  #oceanbites  we are featuring Hannah Collins  @hannahh_irene  Hannah works with marine suspension feeding bivalves and microplastics, investigating whether ingesting microplastics causes changes to the gut microbial community or gut tissues. She hopes to keep working
  • by oceanbites 5 months ago
    Leveling up - did you know that crabs have a larval phase? These are both porcelain crabs, but the one on the right is the earlier stage. It’s massive spine makes it both difficult to eat and quite conspicuous in
  • by oceanbites 5 months ago
    This week for  #WriterWednesday  on  #Oceanbites  we are featuring Cierra Braga. Cierra works ultraviolet c (UVC) to discover how this light can be used to combat biofouling, or the growth of living things, on the hulls of ships. Here, you
  • by oceanbites 5 months ago
    This week for  #WriterWednesday  at  #Oceanbites  we are featuring Elena Gadoutsis  @haysailor  These photos feature her “favorite marine research so far: From surveying tropical coral reefs, photographing dolphins and whales, and growing my own algae to expose it to different
  • by oceanbites 6 months ago
    This week for  #WriterWednesday  on Oceanbites we are featuring Eliza Oldach. According to Ellie, “I study coastal communities, and try to understand the policies and decisions and interactions and adaptations that communities use to navigate an ever-changing world. Most of
  • by oceanbites 6 months ago
    This week for  #WriterWednesday  at  #Oceanbites  we are featuring Jiwoon Park with a little photographic help from Ryan Tabata at the University of Hawaii. When asked about her research, Jiwoon wrote “Just like we need vitamins and minerals to stay
  • by oceanbites 7 months ago
    This week for  #WriterWednesday  on  #Oceanbites  we are featuring  @riley_henning  According to Riley, ”I am interested in studying small things that make a big impact in the ocean. Right now for my master's research at the University of San Diego,
  • by oceanbites 7 months ago
    This week for  #WriterWednesday  at  #Oceanbites  we are featuring Gabby Stedman. Gabby is interested in interested in understanding how many species of small-bodied animals there are in the deep-sea and where they live so we can better protect them from
  • by oceanbites 7 months ago
    This week for  #WriterWednesday  at  #Oceanbites  we are featuring Shawn Wang! Shawn is “an oceanographer that studies ocean conditions of the past. I use everything from microfossils to complex computer models to understand how climate has changed in the past
  • by oceanbites 7 months ago
    Today we are highlighting some of our awesome new authors for  #WriterWednesday  Today we have Daniel Speer! He says, “I am driven to investigate the interface of biology, chemistry, and physics, asking questions about how organisms or biological systems respond
  • by oceanbites 8 months ago
    Here at Oceanbites we love long-term datasets. So much happens in the ocean that sometimes it can be hard to tell if a trend is a part of a natural cycle or actually an anomaly, but as we gather more
  • by oceanbites 8 months ago
    Have you ever seen a lobster molt? Because lobsters have exoskeletons, every time they grow they have to climb out of their old shell, leaving them soft and vulnerable for a few days until their new shell hardens. Young, small
  • by oceanbites 9 months ago
    A lot of zooplankton are translucent, making it much easier to hide from predators. This juvenile mantis shrimp was almost impossible to spot floating in the water, but under a dissecting scope it’s features really come into view. See the
  • by oceanbites 9 months ago
    This is a clump of Dead Man’s Fingers, scientific name Codium fragile. It’s native to the Pacific Ocean and is invasive where I found it on the east coast of the US. It’s a bit velvety, and the coolest thing
  • by oceanbites 10 months ago
    You’ve probably heard of jellyfish, but have you heard of salps? These gelatinous sea creatures band together to form long chains, but they can also fall apart and will wash up onshore like tiny gemstones that squish. Have you seen
  • by oceanbites 11 months ago
    Check out what’s happening on a cool summer research cruise! On the  #neslter  summer transect cruise, we deployed a tow sled called the In Situ Icthyoplankton Imaging System. This can take pictures of gelatinous zooplankton (like jellyfish) that would be
  • by oceanbites 11 months ago
    Did you know horseshoe crabs have more than just two eyes? In these juveniles you can see another set in the middle of the shell. Check out our website to learn about some awesome horseshoe crab research.  #oceanbites   #plankton   #horseshoecrabs 
WP2Social Auto Publish Powered By : XYZScripts.com