Environmental Impacts

The common dolphin (Delphinus delphis) is a very important organism in the marine ecosystem. There are many conservative efforts in place globally to protect these important marine mammals, but there are many types of human interactions that have negatively impacted the common dolphin as well.

Some of the factors that have produced a decline in the common dolphin population are overfishing, bycatch, pollution, degradation of water quality, and climate change. Overfishing is by far the most detrimental to Delphinus delphis (Jackson et al. 2001). Although bycatch and pollution can directly hurt the common dolphin, most of these harmful factors negatively impact the common dolphin indirectly through the depletion and dispersal of its prey (Bearzi et al. 2003). Delphinus delphis diet consists mainly of schooling pelagic fish like anchovies and sardines, which are commonly targeted by fisheries globally.

The decreased population of sardines and anchovies from fisheries result in increased competition between dolphins, sea birds, swordfish, hake, and tuna (Piroddi et al. 2011). This competition produced a decline from 150 to 15 common dolphins that were studied (Piroddi et al. 2011). Therefore, fisheries hurt the common dolphin through an indirect route through the food web. According to a study conducted by Laura Mannocci, over 1000 dolphins are bycaught each year in the Northeastern Atlantic Ocean alone (Mannocci et al. 2012). Bycatch is a mistake made during commercial fishing, where the wrong species of animal is captured unintentionally. This study found that as a result of bycatch at its current pace, Delphinus delphis could decrease in population by 80% in 30 years and become extinct in 100 years in the eastern North Atlantic (Mannocci et al. 2012).

When analyzing global climate change as it relates to ecology, it is important to realize that climate change most prominently affects the common dolphin by disrupting the food web in the dolphin’s marine habitat (Bearzi et al. 2003). The dolphin species themselves are very resistant to many different habitats and temperatures of water, however their prey are not always as resistant. Human pollution can have a direct effect on the common dolphin. The role of toxic pollutants called polychlorinated biphenyls (PCBs) is causing widespread immunosuppression and reproductive problems through biomagnification in the tissues of the Delphinus delphis (Bearzi et al. 2003). These PCB’s are the result of manmade chemicals.

To look at the life cycle of the common dolphin go to History and Reproduction

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