Dolphins in a changing environment

Over thousands of years, food, friends and foes have shaped all aspects of the dolphins’ lives, and many depend on specific habitats. Chilean dolphins prefer shallow, productive, usually sheltered waters very close to shore with input from rivers. This puts them often close to where humans have chosen to live and reap the richness of the sea. Dolphin Picknick off the Panamericana is such an example of dolphins occurring close to human activities. Our long-term study area in southern Chiloé in the heart of Chile’s aquaculture hub is another.

Chilean dolphin off Quemchi - with a navy vessel, an aquaculture vessel, some mussel farms and the beach promenade in the background. (photo: Sonja)

Humans have a long history of exploiting marine resources, even in rugged and inhospitable Patagonia. Native tribes lived off and on the sea, moved around in dug-out canoes, gathered shellfish and hunted otters and sea lions. When Charles Darwin visited Chiloe in 1834 he saw an island completely covered by native forests and swamps where “the forests are so impenetrable that the land is nowhere cultivated except near the coast”. If you visit Chiloé today you drive on fast roads past farmed land, grazed pastures, shrub wasteland, plantations of introduced eucalyptus and human settlements with their associated domestic animals and rubbish. Less than 20% of the original impenetrable southern forests and wetlands remain on the wild western and southern coasts, forming refuges for many endemic species such as the Darwin frog, the Darwin fox, or the pudu (the smallest member of the deer family).

Typical rural landscape of Chiloé (photo: Sonja)

When Jacques Cousteau visited Patagonia in the early 1970s its coast was almost unexplored except for a few settlements and anchorages. If you view Chilean Patagonia from the air today you spot salmon and shellfish farms in pretty much every bay in the Chiloé Archipelago and reaching even into the remotest of the Patagonian fjords. The footprint of our activities and the speed of change have never been as fast, intensive and extensive as in the last 40 odd years, so that is roughly over 3-4 dolphin generation times.

Aerial view of salmon and mussel farms in the Ecoregion Chiloense (photo: Sonja)

Dolphins strive in stable, productive coastal environments but are also well adapted to cope with environmental variability between years (for example El Nino- La Nina oscillations). Populations might struggle when change is rapid, intense and persistent leading to a permanent alteration or degradation of their habitat. Populations will decline in numbers when adult mortality is high and potential for population growth is low. Whales and dolphins are long-lived and slow reproducing (one calf every few years) with extended periods of care for their young. So populations can grow only slowly even under good conditions and are greatly affected by deaths, especially of reproductive females.

Chilean dolphins with a calf - an investment for the future of the species (photo: Sonja)

We’re all familiar with the devastating effects intense whaling had on the large whales, but few are aware of the plight of the many smaller species of dolphins and porpoises. We are currently witnessing a desperate last attempt to save the vaquita, the little desert porpoise in the Upper Gulf of California, Mexico, from extinction. Only 30 individuals are thought to remain, and too many still die entangled in (now illegal) fishing gear. If these last ditch efforts fail the vaquita will join the baiji (the Yangtze river dolphin in China) as the second cetacean species to go extinct entirely due to human activities. That’s a very sad record indeed!

Many other porpoise and dolphin populations around the world, such as New Zealand’s Maui's dolphins, are also in a precarious state, again mostly due to unsustainable levels of bycatch (incidental entanglement in fishing gear). Because of their distribution Chilean dolphins do not generally seem to overlap much with commercial fisheries, but they still can get entangled in coastal fishing nets (for a rare happy ending to an entanglement event see this youtube video here). Of particular concern are intertidal gillnets set by local people to catch fish (often escaped farmed salmon) for their own consumption or local retail. These artisanal nets float at high tide in the shallow intertidal zone which is where Chilean dolphins go to hunt fish such as sardines, robaló or pejerrey. When populations are small, every individual counts. So a very occasional death due to entanglement, even though a rare event in absolute terms, can have serious population consequence….but the occurrence of these events is likely to go unnoticed and unreported, and is thus almost impossible to address.

Intertidal fishing nets such as this one pose a potential threat to Chilean dolphins (photo: Sonja)

Patagonia is still a very thinly populated region with frontier character and few roads. Despite that, the list of human activities potentially harmful to dolphin populations include the ubiquitous issues of bycatch, habitat degradation and loss, permanent changes to the food web that supports them, and contaminants and organic pollutants that compromise health and reproductive potential.

A typical bay that could be liked by Chilean dolphins and that is covered with mussel farms. (photo: Sonja)

The main actors here are fisheries (with nets), and especially aquaculture industries (farming shellfish and fish). The Chilean salmon farming industry has gained a bad reputation for often very poor environmental and health standards. Aquaculture farming affects habitat quality and adds waste, antibiotics, contaminants, non-native species and noise to the coastal marine environments. However, both extractive and cultivating fisheries are key pillars of the Chilean economy, and provide the main employment opportunities in Patagonia (tourism and agriculture are smaller but important sectors). So these activities are there to stay, and people’s livelihoods depend on them. Managing such activities in an environmentally and economically sustainable manner and protecting native species is crucial but remains a very big challenge. At least hunting dolphins for meat and use as bait now luckily seems to be a bad activity of the past, though it might happen sporadically in remote locations where such illegal activities occur out of sight of law enforcement.

Same bay as above but there's also a salmon farm .... (photo: Sonja)

Both magnitude and extend with which human activities in Patagonia affect dolphins (and other marine creatures) remain unknown. We lack basic information on where and how human activities and animals interact, as well as how many animals there were, are now and could be. Such information is vital to evaluate what effects these ever intensifying human activities have had on populations. The dolphins seem to persist in substantially altered coastal environments, but how well are they doing? Our current, IWC funded project is trying to establish some baseline information for the Ecoregion Chiloense (Patagonia) on where the dolphins are and how many there are. Our long-term project in southern Chiloé supported by yaqupacha Germany provides the data to look for trends in the size of one local dolphin population. And last, but not least, Cayetano’s PhD project is looking at novel ways of evaluating health status of Chilean dolphins by using immune response markers and the dolphins' skin microbiome as indicators of health.

Chilean dolphins surface in front of a mussel growth line. Cormorants and terns use the support buoys as a welcome resting platform. (photo: Sonja)