What could be more uplifting for an ocean lover than standing on the emerald edge, sand between the toes, waving goodbye to millions of young fish as they slip into the big blue?
Silhouetted shadows dancing in unison, on a voyage to grow, reproduce and replenish the world’s oceans. Beautiful. Or is it?
Fish restocking sounds like a straight-forward process. Grow fish, release fish, catch fish, repeat. Yet the science behind restocking is anything but simple. In reality, fish restocking is both an art and science, with potential to get it wrong but also every opportunity to be a progressive management and conservation tool. In this article, we delve into why restocking has had a poor reputation in the past and look at why, when managed correctly, restocking forms an essential part of fisheries management and ocean recovery.
First let’s look at the case against restocking. In the past, due to questionable benefits for fisheries, fish restocking has come under scrutiny from parts of the scientific community and fishers alike. A common thread is the lack of evidence that fish restocking works or is cost effective[1].
This lack of confidence in restocking is due to the local release of millions of captive-bred fish that can have negative and unforeseen consequences to the environment. Releasing too many predatory fish in a single area can upset the delicate balance of predator-prey interactions impacting local foodwebs. Similarly, releasing many fish with very similar genetics (brothers and sisters) can reduce the overall genetic diversity of wild populations, leading to higher rates of inbreeding and impacts to survival and fitness of individuals. Additionally, most fish released will never make it to adulthood, falling prey to bigger fish. So then, why should we invest in fish restocking programs if they are expensive, open to failure and could cause more harm than good? Shouldn’t we spend our money on more surveillance, enforcing stricter compliance and better education?
Maybe. But the problem with taking up a defensive position against fish restocking is that it also removes half the ‘tools’ in the fisheries management ‘toolkit’. Surveillance, compliance and education are not particularly good at rebuilding already depleted populations because they focus on preventing fish from being removed from a population, and largely leave the process of recovery up to mother nature. Put simply, these methods are all largely based on a straightforward fisheries equation:
Less fish out = more fish in
The problem with exclusively employing fish-out management solutions to manage and rebuild depleted fish populations is that we are ignoring an entire side of the fisheries equation and leaving much of nature’s rebuilding to chance. It’s like trying to do a push-up with one arm. It’s possible, but only for the select few who have really put effort into it. And with 1 in 10 fisheries collapsed globally, and 50 % over-fished[2], we’re clearly not too good at it. It’s not just fisheries science that suggest we have a bit to learn in recovering natural systems, the field of restoration ecology also tells us that mother nature finds it very difficult to bounce back on her own. So, now let’s look at a slightly different version of the above equation. One that considers restoration and restocking as part of a wholistic fisheries management approach:
More fish in = more fish out
This is where fish restocking and other forms of active intervention like habitat restoration come in. They change the odds of recovery back in favour of enhancing fisheries production. They work on the supply side of fisheries management. When paired with sustainable fisheries management, they can help rebuild depleted fisheries by increasing the number of fish entering a fishery, effectively doubling the number of strategies we can use to rebuild and sustainably manage fisheries.
The practice behind restocking has also come a long way from 20 years ago when it was largely motivated by growing fish as fast and cheaply as possible. Programs are now guided by rigorous science-based decision frameworks[3] and scientific modelling, like that employed by NSW Fisheries[4]. Fish restocking can extend beyond the recovery of predatory fish, to full ecosystem restoration, where the recovery of invertebrates and other important food sources for fish and their habitats can also be restored. Genetic assessments are now cheap and easier to employ, meaning that we can regularly sample entire fish populations to ensure they don’t become genetically poor with restocking activities. Better broodstock management also means that we can select for genetic traits that aid long-term health and resilience. Finally, fish restocking is learning many of the lessons from successful big game reintroductions, where there is lots of evidence demonstrating that conditioning of animals to the receiving environment is an important success factor contributing to survival in the wild.[5]
The ‘art’ is knowing how to bring all of this science together for an effective restocking program and to coordinate recovery with less predictable factors such as floods, droughts and marine heat waves.
It’s this new science and much more that is the foundation of SeaGen Aquaculture’s mission to sustainably and ethically produce fish and marine life for fish restocking and recovery programs. We know that when done well, restocking is a critical tool in ocean management and restoration, complimenting the ‘fish-out’ side of the fisheries equation. Together, fisheries managers have a more complete arsenal in which to appropriately manage fish populations, on the understanding that each species, habitat and management situation is different. Fish restocking is one method that can help tilt the balance away from long-term decline back towards recovery and abundant marine life thriving in our oceans.
[1] Aquaculture: https://doi.org/10.1016/j.aquaculture.2010.05.036
[2] Global Fishing Index 2021: https://www.minderoo.org/global-fishing-index/
[3] Reviews in Fisheries Science: https://doi.org/10.1080/10641262.2010.491564
[4] Reviews in Fisheries Science: ttps://doi.org/10.1080/10641262.2013.796815
[5] Conservation Biology: https://doi.org/10.1046/j.1523-1739.2000.99326.x