Nav: Home

Has protecting marine species become a job for statisticians?

November 08, 2017

Fishermen have no way of separating the fish they catch when they cast their nets at sea. Protected species and fish with no market value -- the hammerhead shark, for example -- end up being trapped and dying for no reason. In an attempt to minimize this incidental fishing, statisticians from the University of Geneva (UNIGE, Switzerland), Dalhousie University (Halifax, Canada) and the Australian National University (Canberra) have devised a new statistical method for predicting bycatches more accurately in the future. The technique, which is explained in full in the journal Annals of Applied Statistics, can also be applied to other research fields, including health economics, medicine and educational science.

When fishermen set out on their expeditions at sea, protected species are caught up accidentally in their nets alongside the fish intended for sale. Biologists are collecting datasets on fish numbers and species conservation figures so they can study the volume of incidental fishing and its impact on marine fauna. The structure of this data, known as "nested", is complex because it integrates a mass of technical information, such as the number of expeditions or the type of boats used. The data also records the amount of protected fish caught in the nets on each fishing trip. However, some species -- the hammerhead shark is one such case -- are usually not caught, making it difficult to establish models that include the number of nil catches for each species. "Until now, there has been no general statistical method that combines a nested data structure with a large quantity of zeros in the observations", explains Eva Cantoni, professor at the Research Center for Statistics at UNIGE's Geneva School of Economics and Management (GSEM). "So this gap needed to be filled, which we did by setting up a very general and flexible model, called the Random-Effects Hurdle Model."

The complexity of generality

The statisticians developed a new method with the ultimate goal of introducing managed fishing and reducing bycatch. "We had to take a range of dynamics into account," continues Cantoni. "The aim was not just to analyse the changes in the number of catches over time but also to study the different seasons and the weather, all the while factoring in the technical conditions: the depth of the nets, the seasons (as I've already mentioned), the type of hooks used, whether light sticks were used or not, and the kind of vessel." Based on this data, the researchers identified the easily influenceable conditions (such as the depth of the hooks) that would reduce the volume of non-marketable species that are caught.

The statisticians then created a new methodology that combined older models specialising in either nested structures or zero management. "The difficulty lay in bringing these two aspects together while ensuring the model was as general as possible so that it could adapt to many situations," says Joanna Mills Flemming, from the Department of Mathematics and Statistics at Dalhousie University. The more general a model is, the more complex it is to process. Modern simulation techniques were used to estimate the model's parameters (related, for example, to the depth of the hooks) and their variability. The authors demonstrated theorems that determine and quantify the margins of error for the model and its predictions. Preventing incidental catches and supporting environmental policy. This modelling means it is now possible to estimate potential bycatches for a fishing expedition. "When fishermen give us their voyage data, we can predict the incidental catch for hammerhead sharks, for example, with more precision," states Cantoni. "The method can be used to back up environmental policies by prohibiting fishing at a certain depth at a particular time of year since it would involve too much bycatch," adds Alan Welsh from the Australian National University.

The model fills a statistical gap: previously, there was no general model capable of simultaneously factoring in complex and nested data structures and a high number of observations equal to zero. Today, the new model does not just serve commercial fishing: it can also be used in other areas with complex data structure, including health economics, medicine and educational science.

Université de Genève

Related Fishing Articles:

How smart, ultrathin nanosheets go fishing for proteins
An interdisciplinary team from Frankfurt and Jena has developed a kind of bait with which to fish protein complexes out of mixtures.
Fishing less could be a win for both lobstermen and endangered whales
A new study by researchers at Woods Hole Oceanographic Institution (WHOI) found that New England's historic lobster fishery may turn a higher profit by operating with less gear in the water and a shorter season.
'Pingers' could save porpoises from fishing nets
Underwater sound devices called 'pingers' could be an effective, long-term way to prevent porpoises getting caught in fishing nets with no negative behavioural effects, newly published research suggests.
Fishing can disrupt mating systems
In many fish species body size plays an important role in sexual selection.
Oversight of fishing vessels lacking, new analysis shows
Policies regulating fishing in international waters do not sufficiently protect officials who monitor illegal fishing, the prohibited dumping of equipment, or human trafficking or other human rights abuses, finds a new analysis by a team of environmental researchers.
Microplastics from ocean fishing can 'hide' in deep sediments
Microplastic pollution in the world's oceans is a growing problem, and most studies of the issue have focused on land-based sources, such as discarded plastic bags or water bottles.
Neither fishing tales nor sailor's yarn
An international team led by Robert Arlinghaus from the Leibniz Institute of Freshwater Ecology and Inland Fisheries and the Humboldt-Universität zu Berlin have developed a method for combining the empirical knowledge of fishery stakeholders in such a way that the result corresponds to the best scientific understanding.
Lights on fishing nets save turtles and dolphins
Placing lights on fishing nets reduces the chances of sea turtles and dolphins being caught by accident, new research shows.
Another casualty of climate change? Recreational fishing
Another casualty of climate change will likely be shoreline recreational fishing, according to new research.
Longline fishing hampering shark migration
Longline fisheries around the world are significantly affecting migrating shark populations, according to an international study featuring a University of Queensland researcher.
More Fishing News and Fishing Current Events

Trending Science News

Current Coronavirus (COVID-19) News

Top Science Podcasts

We have hand picked the top science podcasts of 2020.
Now Playing: TED Radio Hour

Listen Again: The Power Of Spaces
How do spaces shape the human experience? In what ways do our rooms, homes, and buildings give us meaning and purpose? This hour, TED speakers explore the power of the spaces we make and inhabit. Guests include architect Michael Murphy, musician David Byrne, artist Es Devlin, and architect Siamak Hariri.
Now Playing: Science for the People

#576 Science Communication in Creative Places
When you think of science communication, you might think of TED talks or museum talks or video talks, or... people giving lectures. It's a lot of people talking. But there's more to sci comm than that. This week host Bethany Brookshire talks to three people who have looked at science communication in places you might not expect it. We'll speak with Mauna Dasari, a graduate student at Notre Dame, about making mammals into a March Madness match. We'll talk with Sarah Garner, director of the Pathologists Assistant Program at Tulane University School of Medicine, who takes pathology instruction out of...
Now Playing: Radiolab

What If?
There's plenty of speculation about what Donald Trump might do in the wake of the election. Would he dispute the results if he loses? Would he simply refuse to leave office, or even try to use the military to maintain control? Last summer, Rosa Brooks got together a team of experts and political operatives from both sides of the aisle to ask a slightly different question. Rather than arguing about whether he'd do those things, they dug into what exactly would happen if he did. Part war game part choose your own adventure, Rosa's Transition Integrity Project doesn't give us any predictions, and it isn't a referendum on Trump. Instead, it's a deeply illuminating stress test on our laws, our institutions, and on the commitment to democracy written into the constitution. This episode was reported by Bethel Habte, with help from Tracie Hunte, and produced by Bethel Habte. Jeremy Bloom provided original music. Support Radiolab by becoming a member today at     You can read The Transition Integrity Project's report here.