Restocking of Marine Species Must be Completed with Care

Just as human groups acquire determinate characteristics after living several years at the same place, animals acquire genetic particularities, which are not usually considered when planning the restocking of places where a species gets scarce, said biologist Edna Márquez, from the Animal Biotechnology Group at the Universidad Nacional de Colombia in Medellín.

"We analyzed three species bicolor damselfish (Stegastes partitus), red porgy (Pagrus pagrus) and queen conch (Strombus gigas Linnaeus).  The former is affected by a great density problem, because the concentrations diminished considerably within the San Andrés, Providencia and Santa Catalina archipelago, as well as in the continental Caribbean region. For this reason, populations are more exposed to endogamy and to a lost of genetic variation."

The researchers studied genetic variations among the populations settled in diverse areas of the maritime geography. The winkle"s case is a critical one, because in order to improve the density within the banks the populations were relocated. According to the researcher, these solutions may be harmful, because the patterns of the genetic variations remain unknown.

There is a risk of polluting the reserves of each natural region by introducing indiscriminately non"suitable genes to a population. This can alter ecosystems and, in some cases, lead to the extinction of natural reserves. Through conservation work, this situation may be prevented.

The biologists say that the descendents (genotypes) of "non"native" species may greater than the ones from the local species, which would lead to a hard competition for food and territory. Another unwanted effect could be the spread of infectious and parasite diseases. The queen conch, Coccidio apicomplexa, has a parasite linked to low reproduction. If such an organism would extend among various populations, it could affect them, because the majority is not prepared to fight it.

According to the study, the red porgy and the queen conch don"t have homogeneous populations in zones where there should be a genetic link. This is happens in the San Andrés and Providencia archipelago. The queen conch from the north is the different from the one settled on the south.
"It"s indispensable to clarify that each reserve has various populations, distant from each other. In those cases, they could be relocated because their characteristics are very similar. But a winkle from the Jamaica genetic stock should not be put together with one from San Andrés."

It goes the same with fishes and winkles stocks in the Caribbean littoral. The mollusk population around the Rosario islands, in Cartagena, is related with one settled in the south of the San Andrés Archipelago. On the contrary, is not related at all with one from the San Bernardo Archipelago, located at the Gulf of Morrosquillo, on the coast of the Bolivar Department.

In the case of the queen conch, in the Rosario islands, as well as in the south of the archipelago, concentrations have diminished considerably. In those places there is a great mollusk exploitation|. On the contrary, the population is more important in the northern frontier of the Colombian Caribbean Sea.

The physical differences are also noticeable. Morphometrics (form and size) on the porgy, L. synagris, show variations between Santa Marta and La Guajira groups. Regarding the queen conch, the researchers used geometric morphometrics (tridimensional measurement), and found disparities in the shape of the shell between the San Bernardo (Bolivar) species and other species settled at the continent and at the archipelago.

Studies, such as the one from the Universidad Nacional de Colombia, could help to restock the fishes, bearing in mind more complete elements respecting fish and winkle native species.