Tag Archives: ocean

Refining Nemo: Musings from the Australian Society of Fish Biology Conference

The Australian Society of Fish Biology's 2018 Conference delivered some of the most engaging, intriguing talks I've had the pleasure of witnessing

As a fish ecologist living in Norway, it’s a joy to be able to travel to Melbourne and interact with the people that are driving forward fish science in my home country. So when I found out that the Australian Society of Fish Biology’s annual conference was taking place 3 days after my first flight home since 2016, I knew it was an opportunity I couldn’t pass up.

We’re on the last day of the conference at the moment, and over the next 2 months I’m looking forward to bringing you a number of insights, including interviews with guest speakers Eva Plaganyi and Gretta Pecl and pioneers of intriguing projects like Peter Unmack and Jarod Lyon. I’ll also have a fish edition of The Changing Face of Ecology, and some articles on how the angling community and the fish science community interact in a country with one of the most unique fish assemblages in the world.

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The Chilly Cradle of Life

Species richness is much higher in waters near the equator, but do we see that in a phylogenic tree?

Species richness is much higher in waters near the equator, but do we see that in a phylogenetic tree? (Image Credit: Rich Brooks, CC BY 2.0)

An inverse latitudinal gradient in speciation rate for marine fishes (2018) Rabosky et al., Nature  doi:10.1038/s41586-018-0273-1

The Crux

The tropical regions of the Earth are the most species-rich and diverse ecosystems on the planet, with this diversity and species-richness declining as you move further and further from the equator. One hypothesis explaining this is that speciation rates are simply higher in the tropics, meaning that more species are evolving in a given time in the tropics than anywhere else. To test for this, the authors used the largest phylogenetic tree available and analyzed speciation rates (how many new species evolve from older species) per million years.

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The Red King Crab

The Red King Crab has been invading Norwegian waters over the last 50 years

“… a red army of monster crustaceans – marshaled by Soviet-era leaders – is threatening to invade Western Europe …”

– James Owen, National Geographic, 2004

Ominous. That’s the thing, isn’t it. Some invasive species look harmless. You can’t be scared of a baby Canada Goose, can you? Or a nice purple garden flower. Such florescence. You can, however, be scared of a spiny, alien-looking 10 kilo mass of spines and pincers that has been shuffling its way into Norwegian waters over the last half-century.

What are they?

Paralithodes camtschaticus, the Red King Crab, is the most heavily fished crustacean in Russian seas. They fetch a high price at the market, and over 50 million USD was made in exports in Norway alone in 2016. A common trait amongst invasive species, they are a generalist predator, and will eat anything, from small invertebrates to large echinoderms and bivalves. They are among the largest arthropods living, with 8 legs, 2 pincers, a carapace of around 22cm, and an unholy mass of mandibles and spines to go with it. They are also quick movers, and can relocate based on available food quickly. Basically, if I were a sea urchin, were it not for the sea urchin’s general lack of the concept of fear or any other emotion, I’d be terrified.

The current distribution of the crab (top) and the area it will likely spread to in the Barents Sea over the coming years

The current distribution of the crab (top) and the area it will likely spread to in the Barents Sea over the coming years, demarcated by the 0-4 degree zone (bottom) (Image Credit: Christiansen et al., 2015)

How did they get here?

The crab is native to the northern Pacific Ocean, but like the Pink Salmon, they were deliberately stocked into the Murman coast by Russian scientists for commercial fishery. Since the 60s the crab has spread into Norwegian waters, and was well established in Northern Norway by the 90s. Soon after this the population skyrocketed, and the majority of fjords in Northern Norway are now occupied by the crab. Whilst the crabs prefer colder temperatures, increased temperature doesn’t seem to be a barrier for migration, and the fact that there are also reports of human introductions as far south as Bergen should be worrying.

What do they do?

Their role as a large predator of pretty much anything, combined with the fact that they migrate between different depths and are fast movers, mean that they can significantly change the physical structure of the ecosystem that they inhabit very quickly. Their removal of larger bivalves and echinoderms has lead to lower diversity and abundance in Norwegian fjords, particularly among species with low motility, and subsequent changes in the entire community composition of an ecosystem. They can also contribute to a loss in production and nutrient recycling, and subsequent drops in populations of local fish.

Here we see a Red King Crab singing along to YMCA by The Village People

Here we see a Red King Crab singing along to YMCA by The Village People (Image Credit: Creative Commons)

How do we stop them?

This is difficult, and marks the point in this series where we need to actually consider the term ‘invasive’. So far, I’ve considered invasive species as alien species which demonstrate a negative effect for the ecosystems they are novel to, or on the economy of a nation, with no pronounced positive effects in any other aspect. However in many international and national laws, invasive species are those which have a negative impact on human health or economy. And here lies the issue. Whilst the Red King Crab has an undeniably negative effect of local biodiversity, it has a undeniably positive effect on the Norwegian economy.

I’ll return to this topic next week, but for now let’s approach the issue as if we want to stop the incursion. The crabs seem to display high site loyalty, which means that they’re theoretically easy to prevent from spreading further down the Norwegian coast, given correct management. The crabs prefer cold waters so let’s keep that climate change going and drive them out of Norway oh dear God my apologies that’s a terrible idea.

Reducing supply-and-demand lessens the crab’s economic value, so avoiding crab meat is a good step. Yet the Norwegian government’s tactics here are more likely to make a difference. Currently the practice is to maintain a certain capacity in some areas, whilst aiming for fishing to eradication in areas further south to prevent spreading. However there is little incentive for fishermen to eradicate a substantial part of their livelihood, so these regulations may need to be more strictly enforced, or the quota regulated areas restricted further.

For more information on the crab, we invite you to read the following articles.

Giant Crab ‘Red Army’ Invades Norway by James Owen for National Geographic News

Invasive Alien Species Fact Sheet –Paralithodes camtschaticus by the Online Database of the North European and Baltic Network on Invasive Alien Species

Current Status of the Red King Crab and Snow Crab Industries in Norway by Lorentzen et al.

Thermal behaviour and the prospect spread of an invasive benthic top predator by Christiansen et al.

The Case for Environmental Optimism

Almost a year ago, the current President of the United States pulled out of the Paris climate agreement. At that point, the scientific community, climate change activists, and anyone with a passing interest in science (and, you know, the survival of our species) could have been forgiven for thinking that we had finally forsaken our planet. Yet at the STARMUS Festival last year in Trondheim, I was particularly struck by American coral reef biologist Nancy Knowlton’s words on Earth Optimism, and why all may not be lost just yet.

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