Section III - Ecology

Abalones are density dependent animals. The eggs or sperm are released through the pores with the respiratory current. This is known as broadcast spawning. A 1.5-inch abalone may spawn 10,000 eggs or more at a time, while an 8 inch abalone may spawn 11 million or more. The water temperature or length of the day may control spawning. Grazing and reproduction usually occupies most of the life of an abalone. Dolphins are density independent. In almost all cases, only a single calf is born; twins are rare, and it is highly unlikely that both would survive. Gestation lasts 10-12 months. The calves are fully developed and unlike other mammals, the calves are generally born tail first, in the "breech" presentation; sometimes the calves are already visible for some time before the rest of the body follows.

Abalones are opportunistic when they spawn. Producing as much possible as they can, while dolphins have an equilibrium life history. The mother can only tend to one calf at a time. Both the abalone and the dolphin can be found in an aquatic ecosystem.

Abalone on the Pacific coast are found on rocky intertidal and subtidal areas from Baja California to Alaska. Each species prefers a particular habitat which appears related to the local sea temperature. For instance, in cold northern California they may be found intertidally (the area between high and low tide), whereas in warmer southern California they usually occur subtidally (in the water below the low tide mark). Small abalone seek cover in crevices, under rocks or in spines of sea urchins. This behavior probably results from an abalone’s instinctive attraction to dark places, which protects them from many predators. Though small abalones hide during daylight hours, they are active at night.

Geographical distribution for the dusky dolphin is usually limited to the temperate waters of the Southern Hemisphere, especially off of New Zealand, South America and Africa. These acrobatic, inshore dolphins are rather easy to approach. They ride bow waves, frequently breach and perform complete somersaults after feeding.

Marine algae is the main food source for the abalone. The adults feed on loose pieces drifting with the surge or current. Large brown algae such as giant kelp, bull kelp, feather boa kelp and elk kelp are preferred, although most others may be eaten at various times. Abalones tend to stay in one location waiting for food to drift by. However, they will move daily, seasonally or when food becomes scarce for a long period.

Throughout its life an abalone contends with a variety of predators. The eggs and larvae are eaten by filter-feeding animals. And although the juvenile hide, they are active at night and crabs, lobsters, octopuses, starfish, fish and predatory snails prey on them. Large abalone are not threatened by the predators of their earlier life, but larger, and often more efficient predators, now become important. Fishes, such as the cabezon, can dislodge some abalone and swallow them whole. Even very large abalone are no match for the crushing jaws of a bat ray. The sea otter is the most effective predator, capable of removing all exposed abalone within reach. Abalone are one of the first food items taken by otters as they move into new habitat.

The dusky dolphin prefers to eat anchovies, squid and schooling shrimp. While feeding, they seem to use noisy body slams as a way of herding fish and also to alert other dolphins of the feeding opportunity as they like to feed as a group.

There are no main predators for the dolphin. This is partly because of their speed and agility. Humans are the main cause for their deaths. As dolphins feed on fish, they cause a problem to those trying to catch the fish. The dolphins get caught in the net and most of the time the fishermen just end up killing them.

The abalone are considered to be a primary consumer as they eat algae which is a producer. Dolphins could be considered a secondary or tertiary consumer on the trophic level. They eat fish, which also eats smaller consumers.

The dusky dolphin and the northern abalone, though found in the same ecosystem, do not interact with each other. The ecosystem would not be greatly affected if either organism would become extinct. They both have numerous types of species under the same genus that live and act the same way they would in the ecosystem.