Wearable fitness technology has been a burgeoning industry over the last few years, but now the idea is extended to wildlife – especially of the fishy variety. The Pacific Northwest National Laboratory has developed a new ‘Lab-on-a-fish’, a tiny sensor which can provide in depth knowledge about the health and activity of environmentally and commercially significant fish species.
Dubbed by some as the ‘fitbit for fish’, the PNNL’s biosensor can simultaneously gather information about specific fish over a wide variety of variables. It is able to measure the location, heartbeat, tail movement and activity level of the fish, as well as the temperature and pressure of the water they are swimming in. All of this information is vital to understanding the health and stress levels of fish as they travel through different areas of river systems – some of which have been affected by human activity. This information can then be used by marine biologists, hydroelectricity developers and aquaculture operators to better develop strategies for management and conservation.
This is not the first time tags have been used on fish, but previous designs have usually only recorded one specific variable. Meanwhile, the Lab-on-a-fish employs multiple sensors but on a device small enough not to negatively impact the fish. The current model only weighs 2.4 grams and is around the size of a pen cap, meaning it can be used on smaller fish species.
To function, the sensor is surgically inserted under the skin near the fish’s rear dorsal fin. It then wireless sends information to a receiver via a series of beeps. Once the information is received, either wirelessly or from the device itself, the beeps are passed through a machine learning algorithm which condenses the raw information into figures the researchers can use in their studies. There is enough battery life within the sensor to provide information for up to eight months.
To date, the team has conducted trials in a laboratory environment with three species of fish: rainbow trout, white sturgeon, and walleye. However, its applications could be extended to a wide number of important species of river fish. Of course, deploying the sensors in the wild may provide additional challenges, especially in regards to maintaining contact with the tagged fish and possibly retrieving the sensors.
But the information received could then be used to better assess the stress levels of fish at different points in their migrations and travels. In particular, it can be used to determine the impact, if any, human commercial and energy generation activity has upon the natural rhythms of certain fish species.
Hydropower: Good for Us, Bad for Fish?
Although hydroelectric dams can provide a huge amount of renewable energy, they have recently come under renewed scrutiny in terms of their impact on fish species. Large scale damming projects in North America have heavily depleted the numbers of salmonids, while damming of China’s Yangtze river likely contributed to the extinction of the Chinese paddlefish. Not only does this have an ecological impact, but it also affects the livelihoods of locals who depend on aquaculture for a living. This issue is especially true in the Global South, which is currently undergoing a large number of hydroelectric projects.
As well as being killed in hydroelectric turbines, dams can separate fish from their spawning grounds and upset the natural life cycles of entire species, especially those which swim upstream to reproduce. Many man-made obstacles now include ‘fish ladders’ to facilitate upstream movement around obstacles. Traditional fish ladders usually consist of a series of small steps fish can jump up, but larger modern hydroelectric dams present new challenges. To combat this new, slightly more unusual designs have been attempted, including elevators which lift fish up in hoppers, or pneumatic cannons which suck fish up one end and fire them out the other.
However, the effectiveness of these devices is debated. They should be designed so as not to overly exert fish, leaving them with enough energy to continue their tough upstream journey, but this cannot always be guaranteed. One US study suggested only three percent of shad made it to their spawning grounds via all the fish ladders on their route. The biggest issue to developing effective fish ladders is the lack of reliable swimming data about the fish themselves. Although laboratory tests can be conducted, they are often of questionable validity compared to fish living in the wild. Hopefully, new innovative biosensors, like the Lab-on-a-fish can help develop better strategies for making fish-friendly hydroelectric power.
