//
you're reading...

Aquaculture

Cascading Effects From Geoduck Expansions

Article: Ferriss, B. E., Reum, J. C., McDonald, P. S., Farrell, D. M., & Harvey, C. J. (2016). Evaluating trophic and non-trophic effects of shellfish aquaculture in a coastal estuarine foodweb. ICES Journal of Marine Science: Journal du Conseil, 73(2), 429-440. DOI: 10.1093/icesjms/fsv173

Figure 1: The Pacific geoduck (Panopea generosa) is a popular bivalve beloved by many seafood connoisseurs. Its edible popularity has spawned a huge aquaculture business in the Pacific coast. Credit: Flickr https://www.flickr.com/photos/viucsr/6926921010

Figure 1: The Pacific geoduck (Panopea generosa) is a popular bivalve beloved by many seafood connoisseurs. Its edible popularity has spawned a huge aquaculture business on the Pacific coast. Credit: Flickr

Today is the last day in our “All About Aquaculture” theme week; by now, you have read a lot about the benefits, troubles, and unique species associated with “farming” ocean critters. But how does cultivating a species in a designated area affect the food web?

The ecosystem model Ecopath with Ecosim (EwE) is a tool used to look at specific tropic effects in foodwebs, such as their role of bivalves as prey. But what about non-trophic effects such as competition for space? EwE can look at mediating effects, the underlying processes that cause the observed effect between organisms in an ecosystem. For example, how does the concentration of a tasty prey source in one area (such as aquacultured shellfish) alter that ecosystem’s predator structure?

In Washington State, geoduck (pronounced gooey-duck) aquaculture (Figure 1) is an over 10 million dollar industry! It can take 5 to 7 years for a single geoduck to get from its larval size to market size, so a significant effort is taken to reduce predation. In the early stages, geoduck “seed” is protected from predation by placing them in net-covered PVC pipes (Figure 2). This change in the benthic habitat type is likely to change predator-prey interactions and ultimately have effects on this ecosystem by changing which predators will be present.

The Approach

Figure 2: A geoduck farm uses PVC with netting to protect young geoducks from predators. This can alter the bottom habitat-type, changing the type of predator it attracts. Credit: Wikimedia https://upload.wikimedia.org/wikipedia/commons/e/e8/Geoduck_Farm_on_Hartstine_Island.jpg

Figure 2: A geoduck farm uses PVC with netting to protect young geoducks from predators. This can alter the bottom habitat-type, changing the type of predator it attracts. Credit: Wikimedia

The EwE model is an open source and free software that allows users to create ecosystem models for specific areas or to adapt pre-existing models to address specific ecological questions. A Puget Sound-specific EwE model was adapted to predict the effects expanding geoduck aquaculture could have on the ecosystem.

Essentially, the Ecopath part of EWE balances gains and losses in biomass (the total weigh present of an organism) by looking at parameters such as diet, mortality, production (photosynthesis), and consumption (predation). Ecosim allows the modelers to predict temporal-based changes to a foodweb by including factors such as harvest, immigration, and emigration.

Mediation effects are complex since they can have positive and negative effects on ecosystem dynamics. For example, increasing eelgrass biomass (a habitat type) could positively affect juvenile salmon biomass by allowing more prey and negatively affect juvenile salmon by increasing refuge space for predators of salmon. For geoducks, the mediation effects are mostly related to the PVC anti-predator structures (Figure 2).

The effects geoduck aquaculture has on the Puget Sound ecosystem were analyzed in two approaches. First, the carrying capacity of geoducks was estimated (just how big a single organism’s population can get before it will negatively affect other organisms). In a marine system, this is often related to phytoplankton production. Secondly, the trophic and non-trophic effects of an increasing geoduck industry were estimated on other functional groups (predators, prey, and other organisms).

What did they find?

Figure 4: Great blue heron populations where estimate d to decline by 23% due to changes in fish populations causes by geoduck aquaculture. Credit: Audubon http://www.audubon.org/sites/default/files/Great_Blue_Heron_m17-57-218_l_0.jpg

Figure 3: Great blue heron populations where estimate d to decline by 23% due to changes in fish populations causes by geoduck aquaculture. Credit: Audubon

Purely looking at carrying capacity (no mediating effects), the current geoduck aquaculture industry could increase by 120% without affecting the Puget Sound ecosystem. The current day geoduck standing stock was estimated to be at only ~0.1% of the maximum carrying capacity.

That is neat, but that estimate is only considering geoducks and not the interconnected effects this increase would have on the entire ecosystem. So next up was to look at the trophic interactions, without any mediating effects. It turns out, that 120% increase also would have little effects, since there was plenty of phytoplankton to go around. Additionally, there was only a predicted 2% increase in the two biggest geoduck predators, sea stars and the Dungeness crab, and a <1% increase in the other major critters in the Puget Sound biomass.

Here is where this picture changes: when mediating effects (effects not directly tied to trophic interactions) are taken into consideration, huge changes are simulated. That 120% geoduck increase was associated with increases in other Puget Sound organisms. For example, Great Blue Herons, a top predator, were predicted to decrease by 23%, while the Pacific cod increased by 7% (Figure 3).

The PVC anti-predator guards for geoducks were modeled to have a large influence on the type of predator that thrived in Puget Sound, the effects of which propagated up the food web. The PVC caused an increase in demersal fish (bottom-dwellers), which altered the prey type available for the even bigger predators. In other words, this change in fish-type caused bird populations to suffer due to a lack of their preferential food source, observed as a decrease in small crustaceans.

The Significance

Including mediation effects, such as changes in predator refuges, can greatly improve ecosystem modeling. Aquaculture is almost certainly going to increase in Puget Sound as demand for geoducks (and other organisms) increase. Better understanding which marine organisms and functional groups (demersal vs flatfish) could be affected is important so we can better monitor these vulnerable organisms to inform better management decisions, such as restoring a certain habitat type that may encourage declining organisms to recover.

Discussion

No comments yet.

Post a Comment

Instagram

  • by oceanbites 3 weeks 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 1 month 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 3 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 3 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 3 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 3 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 4 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 4 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 4 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 5 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 5 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 5 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 6 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 6 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 7 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 7 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 8 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 8 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 9 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 
  • by oceanbites 9 months ago
    Feeling a bit flattened by the week? So are these summer flounder larvae. Fun fact: flounder larvae start out with their eyes set like normal fish, but as they grow one of their eyes migrates to meet the other and
WP2Social Auto Publish Powered By : XYZScripts.com