Monday, February 29, 2016

Why do we not care about fish?

In June 2015, the whole world got to hear about the death of the lion Cecil in Zimbabwe, by an American recreational big-game hunter, i.e., someone who kills big animals for fun. The whole idea of killing animals for fun seems distorted and out of place in our days, but this is a market that still generates millions of dollars a year. Every year, perhaps thousands of large animals, like lions, rhinos and giraffes are hunted by people who appreciate and can afford this dubious and expensive type of fun. A study has estimated that annually an average of 244 lions only are hunted in Africa! What was different in the case of Cecil is that he was a lion being studied and tracked during years by researchers from the University of Oxford. When his killing made the international news (you can guess that the large majority of hunted animals never does), we got to see what I remember as one of the most intense conservationist reaction by the general public in my life time. People were just outraged by the unnecessary death of Cecil, and as a response, some airlines voluntarily decided to ban the transport of hunting trophies (basically the heads of the dead animals), while the USA added two lion sub-species to their list of endangered species, making it harder to American citizens to kill these animals. On the other hand, Namibia said that such a negative response to hunting would impact the conservation efforts in their country, as they use the money from the hunting market to support their conservation initiatives. Perhaps the times have changed and Namibia will find out that it is possible to make as much, if not more money by letting people watch live animals in nature, as long as the country is stable and safe to visit. The topic is controversial nonetheless and there is no easy answer to whereas there can be sustainable trophy hunting.

Photo from

While this is all good and we are happy that there is such a concern for nature slowly brewing in society, this is still a blog about fisheries, right? Many of us that care about fisheries probably realized that society is ready to take responsibility for the charismatic animals, such as lions, but not yet for fish. In a timely piece on Animal Conservation, Costa-Pereira pinpointed with accuracy such mismatch between our conservation interests and the unlucky less charismatic fish species. Most people do not see anything wrong with recreational fisheries and for that we will go on posting pictures of ourselves holding large and, sometimes, endangered fish species in our social media. This will still be cool for decades to come. Worse than that, we will keep discarding almost a third of our catches in the oceans, because we never intended to catch them in the first place. 
Perhaps we are being too impatient and we should take one step at a time: today Cecil, tomorrow swordfishes, and perhaps one day we will just care for all creatures equally. When this day comes, how many fish species will have been lost for good?

by Priscila Lopes

Monday, February 8, 2016

Artificial selection: are humans driving non-intentional evolution in animals?

For years, fish scientists have alerted about the dangers of establishing a minimum fish size for a given species, as a way to assure that fish makes it at least through its first reproduction, disregarding regulations about a maximum size as well. But the topic has finally made the news. In an interview to BBC,Professor Adam Hart explained that we have for millennia intentionally selected size and other features of our domesticated livestock and plants, which has led to descendent organisms that differ genetically from their ancestors. This change in gene frequency is evolution, and, in this human-induced case, we call it artificial selection. However, not all human selection pressures are as intentional as those imposed by plant and animal breeders. Recent research is revealing that many of our activities exert significant unintentional selection on organisms, which has been labeled as "unnatural selection".

As we let it slip at the beginning of our post, one such example of unnatural selection is what we have been doing to our fish under the auspices of our fishing regulations. We have all (at least the ones reading this post) come to believe that it is wrong to eat small juvenile fish: we should let them reproduce first to assure that we will have more fish in the future. Indeed, there is nothing wrong with such reasoning, the problem is that such measures addresses only half of the problem. As the preferred choice of both fishermen and consumers, the policy of catching large fish and releasing the small ones has been an important tool for managing fish stocks since the 1880’s. With time, policies and regulations have advised the use of larger mesh sizes in fishing nets, as a way of selecting larger fish whilst letting the little ones pass through the gaps. Under most national policies, fishermen have been legally obliged to target large fish and release the smaller ones. Size limits, of course, vary according to the target species.

Photo by Laura Honda

Despite its good intention, targeting the largest fish has consequences: "We have removed the large fish and that has a direct effect on the size structure of a population. Subsequent populations will feel that impact because those smaller fish contribute more genes to the population" said Dr Eric Palkovacs from the University of California Santa Cruz in the same interview to BBC. In other words, the genes for "smallness" prosper while genes for "largeness" are selectively removed by fishing.

In addition to the fact that fish are evolving to be smaller, they are also become sexually mature at a younger age. This is because those fish that have genes causing later maturity are likely to be the largest ones, and, therefore harvested before they have the chance to breed, removing those genes from the population.

Photo by Laura Honda
Photo by Laura Honda
An example of this issue is the North Atlantic Cod, perhaps the most emblematic species in the fisheries literature. This species can reach up to 2 or more meters in length and these giants were common in the 19th century. Nowadays, cods of this size are virtually extinct, they rarely grow beyond 1 meter.
However, developing regulations and technology that give both the juveniles and the larger specimens a chance to survive is not straightforward. We could think of regulations with slots of capture, with a minimum and a maximum size allowed. But how feasible is that? Or perhaps, we could use our understanding of the high fish mortality in the early phases of fish development and target a proportion of juveniles only. But then again: do we really know enough about all fish targets to establish juvenile quotas? Or more seriously: can countries, especially developing ones, really enforce such quotas?
While we wait for the right answers or right regulations, we are probably only worsening a "Darwinian debt" for generations to come.

By Maria Grazia Pennino