Seasons in the Sea - A month-by-month guide to Central California sea life
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Mackerel school: Image credit-Kip Evans

The open ocean

for October

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Diver-at-work symbol (c) Kim Fulton-Bennett This page under construction.
Here are some of the topics that will be covered in this chapter. More text and images will eventually be added to this section. Thank you for your patience.

Open-ocean events in October:

  • Calm weather and warm, layered surface waters in protected areas provide optimum conditions for dinoflagellate blooms (which sometimes result in red tides). Unlike diatoms, which dominate during the upwelling season, when nutrients are plentiful in the surface waters, dinoflagellates can survive when the surface waters contain relatively few nutrients. They do this by swimming down into deeper waters (50-75 feet down) at night to absorb nutrients, then swimming back up to the surface in the daytime to collect sunlight for photosynthesis.
  • Some dinoflagellates (Lingulodinium and Ceratium spp) may be carried into Monterey Bay and other dinoflagellate incubation areas by the relatively warm water surface waters of the Davidson Current.
  • Blooms of a toxic diatom species called Pseudonitschia australis are also common in late fall. These long, narrow (pen-shaped or "pennate") diatoms apparently can survive on less or different types of nutrients than the pill-shaped "centric" diatoms of spring and summer.
  • Worms in the genus Poeobius drift in the deep waters of Monterey Bay (1,000-3,000 feet down) and eat a lot of pennate diatoms in September and October, after these diatoms bloom in surface waters then die off, sinking into the depths.
  • Krill and sardines become somewhat less abundant, but still may form large swarms where food (algae) is available.
  • As krill and sardines become less numerous, many larger animals begin to leave the area, including humpback whales, blue whales, sooty shearwaters, brown pelicans, and summer-nesting birds such as terns and guillemots.
  • In deeper water, small schooling fish called lanternfish (Myctophids) become less abundant, while headlight fish (Diaphus theta) become more abundant.
  • Bluefin tuna are most likely seen in Central California waters (especially offshore waters) during October and November, after upwelling stops and warm oceanic water moves toward shore. These tuna feed along the West Coaast of the US for two to three years then migrate all the way to Japan to spawn
  • Canary rockfish and vermillion rockfish mate in deep water. The young will develop inside their mother's bodies until being released as larvae in spring.
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