Surely I should title this article being much more exact: predatory fish animals, I am convinced that it would be more specific, but since the fish that we constantly treat is a beautiful fish that makes us dream constantly about its fishing, and the diet of its predators can be almost exclusively in rivers where the fish par excellence is trout, I have decided to leave it with this title. You will forgive me for this voluntary slip ...

In the Iberian Peninsula there are five species of animals that in their usual diet include trout and salmon smolts in their weekly menu. Furthermore, in salmon rivers where the predominant species is trout and salmon, these predators attack the fish that are the object of desire of fishermen on a daily basis.

There are three species of birds and two of mammals that are the ones that mainly prey on salmon populations. Here I have omitted mammals such as the Pyrenean Desman and birds such as the Fish Eagle because they are extremely rare species almost in absolute danger of extinction.

The three species of birds are easily recognizable by the fisher reader. The common or great cormorant, the kingfisher and the gray heron. Likewise, the two species of mammals are more than known: the Iberian otter and the American mink.

Thanks to the Natura 2000 reintroduction program, in many Spanish river ecosystems the otter that had disappeared or was very rare, from most of the Pyrenean rivers in my region, was reintroduced with outstanding success. The translocation of specimens from Extremadura at the end of the last century has ensured a stable population that has spread to all the rivers of Catalonia. The reintroduction of the otter has been a complete success.

The otter is the largest of all Iberian mustelids. It is a tremendously territorial animal that bases its diet on fish, whether they be trout from the Pyrenean snow streams to barbels and snook in the lagoons of the river deltas. It is an animal fully prepared for swimming, myopic (not underwater) and almost deaf. It can weigh up to 12 kilos although they often do not exceed 6 or 8 kilos in weight. Great hunter of fish that feeds almost exclusively. It is a very nice animal and totally harmless unless it is attacked and with no possible escape. Native to all the rivers of the Iberian Peninsula and that has been living in the river with our native fish for thousands of years. It preys on medium to good sized trout that it consumes in its entirety after playing with the fish for a long time. No matter how many otters there are in a river or rather how many that can be seen in various sectors, in my opinion it is an animal that does not deplete fish populations, in our case trout or salmon. The otter is an absolutely territorial animal and lives in balance in the fragile river ecosystem.


The American mink is another mustelid much smaller than our otter that was sneakily released from farms by people with a profound ignorance of ecosystems and the damage they have caused to many species of waterfowl among many other animals. This mustelid has been unsuccessfully hunted by the official hunting and fishing services. The damage it provides in fish species is quantitatively very diverse depending on the region where it is found. The american mink feeds on birds such as ducks and redfish, amphibians and reptiles, fish and crustaceans, and other animals such as insects. In certain Spanish regions it has been found that 50% are fed fish, while in Catalonia it does not generally reach 15%. It is an animal that should not be in contact with all our native fauna and that does not enjoy any protection by the law, unlike its cousin the otter who is fully protected.

Among the predatory trout birds, I put in the first place the kingfisher, which is a tiny bird with fine and colorful plumage that hunts fish fry throughout the Spanish territory and in all river environments, whether in the mountains or in the river plains. and the deltas. It mainly predates not only fish fry but also takes its tribute in its roe.

It is a protected species that does not compromise our fish populations at all.

The gray heron, also a protected bird, feeds mainly on fish and crustaceans and that we can observe on the edges of streams and on river banks completely still waiting to pounce with its tremendous and long spear-shaped beak to catch fish and small and medium size trout. In my opinion, its impact on fish populations is very notable, but it feeds mainly on small cyprinids and invasive fish such as alburnos and minnows, which are too abundant in our rivers and which make a disastrous competition in feeding the fry of our beloved common trout. . In rivers whose main species is common trout it can cause considerable damage to fingerling populations, but what must be taken into account is that many of these rivers have indecent populations of minnows on which they also frequently feed as well as signal crab.

Finally it is the turn of the great cormorant that has become a veritable plague in all our river ecosystems. These birds, previously the object of protection (hence their tremendous expansion throughout Europe) and now considered as a non-hunting species, that is, they are not protected but cannot be hunted, their population has increased by one thousand percent and before a devastated marine continental shelf with fewer fish than would be desirable, our rivers have risen to the highest levels of the Pyrenean fluvial ecosystems. The cormorant is a tremendous hunter that feeds almost exclusively on fish and crustaceans, being the first ones for which it has a special predilection and that has become the No. 1 enemy of our populations of common trout and Atlantic salmon. It is a serious problem that must be resolved by the European authorities because it puts at constant risk the fragile stability of the populations of Mediterranean trout and Atlantic salmon. They are birds that know how to hunt both alone and in groups, and when they do, the extent of their predation is devastating. Tremendously smart and intelligent, with their own language since they relate to each other through their own language, they have an innate capacity for submerged swimming, this being their main quality since it can last several minutes without leaving the water to breathe.

The damage they cause to trout and salmon populations is unquestionable since they are capable of swallowing specimens that can exceed one kilogram of weight and that mortally injure specimens that can exceed 4 or more kilos in weight with pecks. The damage they cause is terrible since they hibernate in our rivers in the months of November to March, which is when trout and salmon are in the reproduction period and that is when both species are more vulnerable as they are digging their nests to deposit their eggs.


This problem must be definitely addressed without reluctance by the European authorities and allow a responsible but sufficient hunting, to cushion the irreparable damage that year after year they produce by weakening the already meager stocks in our beloved rivers. It is in no way a question of eliminating a species of bird, but rather of ignoring two other species of fish that are in clear regression and that already have many added problems such as climate change and the lack of sufficient water flows for their survival. .

~ Carles V.