Search
  • richelletanner

Marine life increasingly affected by vessel traffic


This past weekend, I was making a trip back to the mainland from Catalina on USC’s boat, the Miss Christi, when we happened upon a large pod of dolphins within sight of Palos Verdes and the Port of Los Angeles. The boat slowed, and they swam up to ride the bow, jumping alongside us and following the boat as we slowed and continued to the mainland. This wasn’t the first time I had seen marine mammals on a trip to or from Catalina; whales, sea lions, seals, and dolphins are common occurrences during the hour and a half journey from San Pedro to Two Harbors.

With so many sightings on such a short trip, one can only assume that population densities are relatively uniform across the entire channel. However, there is quite a challenge in making sure the populations don’t decrease: the San Pedro Channel and the Southern California Bight in general host two of the largest ports on the west coast, the Port of Los Angeles and the Port of Long Beach. These ports bring in heavy marine vessel traffic both locally and from overseas, meaning conservation laws must take economic gain into consideration when restricting activities in the channel.


Sharing the open ocean

Marine life is abundant in the San Pedro Channel. There are a number of game fish, including sea bass and yellowtail, seals, sea lions, dolphins, sea otters, many kinds of sharks, pilot whales, gray whales, humpback whales, blue whales, orcas, and many more. This diverse ecosystem manages to withstand the pressure of marine vessel traffic, fishing, and pollution to thrive and grow in numbers, due to the nutrient-rich waters carried by the California Current. The most-sighted marine mammals are the dolphins and whales, especially on tours of the channel. Dolphins and whales are not actively monitored by satellite, but whale-watching tours are very popular, especially led by the Aquarium of the Pacific in Long Beach. According to a blog from their website, the tours frequently see fifteen or more whales per trip, in comparison with four or five in previous years. The main whales seen are of the gray, blue, and humpback variety: all protected by the Marine Mammal Act of 1972. Gray and blue whales tend to travel alone, and migrate up and down the shallow waters of the Northeast Pacific Ocean. This makes the Southern California Bight a prime habitat for whales of all sizes, and the channel a perfect place to swim. They eat small plankton or benthic amphipods, depending on the specific species. Humpback whales are more likely to travel in groups, and feed on schooling fish of all kinds. Common dolphins are extremely common in the channel, and can be seen in large pods, catching schools of fish to eat. They are black/gray and white with an unusual hourglass pattern, not to be mistaken with bottlenose dolphins. It is apparent that somehow the marine mammals are thriving, despite our best efforts. Although this is fantastic news for conservation groups and scientists alike, it poses a problem for the ever-growing port economy.


Boat traffic in the San Pedro Channel (top) and the Southern California Bight (bottom). Courtesy of SanPedro.com.

Water contaminants

Storm runoff, ship waste, and ballast waters have the potential to render an ecosystem uninhabitable. Ballast waters are the major problem associated with ships, as they introduce foreign waters and inevitably new and invasive organisms from other ecosystems around the world to an area not accustomed to supporting these animals. They can quickly take over and render native species extinct, if not kept in check. This can mean a decrease in food for dolphins and whales, which can lead to a decrease in their overall populations. Other water contaminants such as bacteria, trace metals, and pharmaceuticals can adversely affect the ecosystem, but are mainly introduced by mainland pollution.

Noise pollution


Shipping lanes (red) and ferry lines (green) in the San Pedro Channel. Courtesy of the Southern California Coastal Ocean Observing System.


Sea lion wounded by a propeller strike heading back out to sea from Two Harbors, CA. Photo by Richelle Tanner.

Ship strikes


In the past week, four sea lions have washed up on the shores of Two Harbors and Cat Harbor – all dead from propeller strikes. Although this is a rare event, it is a reminder of how devastating ship strikes can be for marine mammals. However, whales are the most common victims of ship strikes, with the most confirmed as killed in a year in a single area within the California coastline being four, in 2007. These numbers must be inflated to reflect the true number of whales, as they tend to be negatively buoyant – they often sink to the bottom after being struck and drifting into deeper waters. The number of strikes is higher in the channel due to environmental factors that make the waters more desirable for whales to frequent. The waters in the channel are places of upwelling, full of krill and other food for whales. Coincidentally, they coincide with shipping lanes, making for increased density of both whales and ships in a small area. Whales also dive for their food, often up to 200 meters, and have to rest for long periods of time at the surface – this exposes them to ships passing through.

There is no clear solution to ship strikes, and they continue to increase in numbers as the amount of both ships and whales in the channel grows. Routing ships away from the area would help the issue, but is not economically feasible with the ports nestled along the coast on the other side of the channel. Although it is a difficult decision, we need to distinguish an “acceptable” number of ship strikes that is both economically advantageous and safe for these gentle giants’ populations.

This dilemma is a classic case for effective marine spatial planning. While being a fairly new concept, according to the Ocean Policy Task Force it is the “comprehensive, adaptive, integrated, ecosystem-based, and transport spatial planning process, based on sound science, for analyzing current and anticipated uses of ocean, coastal, and Great Lakes areas”. In order to reduce the number of whale strikes, the stakeholders must reach an agreement in order to view the open ocean as more of a commonplace for all creatures, instead of being a series of exclusive economic zones for humans. Unfortunately, as the number of stakeholders and their wealth/invested capital increases, the whales’ chances for survival decrease. Although it is unreasonable to suggest that all shipping lanes be removed from the San Pedro Channel, policymakers could take into account the migration patterns of common whales in the channel, reducing speed limits when they are more plentiful and allowing more traffic when the whales are elsewhere. The issue with this solution is the rigidness of industry traffic – the consumption of goods does not align with the migration patterns of whales, therefore shortages in some parts of the year will become an issue. There are innumerable arguments regarding who is “in the right” when it comes to sharing the open ocean, but one thing is becoming increasingly clear – without a comprehensive marine spatial planning update to the San Pedro Channel, marine mammals will become increasingly rare.


Bibliography

(2013, July 16). Harbor Information: Los Angeles/Long Beach [Web Graphic]. Retrieved from http://www.sccoos.org/data/harbors/lalb/fullscreen.php

(2013, July 16). San Pedro Marine Traffic Map [Web Map]. Retrieved from http://www.sanpedro.com/marine-traffic-maps/San-Pedro-Marine-Traffic-Map.htm

(2013, July 16). San Pedro Marine Traffic Map Large [Web Map]. Retrieved from http://www.sanpedro.com/marine-traffic-maps/San-Pedro-Marine-Traffic-Map-Large.htm

Au, W. W. L., P. E. Nachtgall and J. L. Pawloski. 1999. Temporary threshold shift in hearing induced by an octave band of continuous noise in the bottlenose dolphin. Journal of the Acoustical Society of America 106:225 l.

Betz, S., Bohnsack, K., Callahan, A. R., Campbell, L. E., Green, S. E., & Labrum, K. M. (2011). Reducing the risk of vessel strikes to endangered whales in the santa barbara channel. Bren School of Environmental Science & Management, UCSB, Retrieved from http://fiesta.bren.ucsb.edu/~whales/pdfs/Whales_Report.pdf

Calambokidis, J. (2011, June). Ship strikes of whales off the u.s. west coast. American Cetacean Society, Retrieved from http://www.cascadiaresearch.org/reports/Calambokidis-ShipStrike-ACS-Qtr-2-11-Issue.pdf

Cross, J. N., Hardy, J. T., Hose, J. E., Hershelman, G. P., Antrim, L. D., Gossett, R. W., & Crecelius, E. A. (1987). Contaminant concentrations and toxicity of sea-surface microlayer near los angeles, california.Marine Environmental Research, 23(4), 307-323. Retrieved from http://www.sciencedirect.com.libproxy.usc.edu/science/article/pii/0141113687900249

Erbe, C. (2002). Underwater noise of whale-watching boats and potential effects on killer whales (orcinus orca), based on an acoustic impact model. Marine Mammal Science, 18(2), 394-418. Retrieved from http://onlinelibrary.wiley.com.libproxy.usc.edu/doi/10.1111/j.1748-7692.2002.tb01045.x/abstract

McKenna, M. F., Ross, D., Wiggins, S. M., & Hildebrand, J. (2012). Underwater radiated noise from modern commercial ships. Acoustical Society of America,131(1), 92-103. Retrieved from http://cetus.ucsd.edu/Publications/Publications/McKennaJASA2012.pdf

Port of Long Beach. (2013). Latest monthly teus. Retrieved from http://www.polb.com/economics/stats/latest_teus.asp

Port of Los Angeles. (2013). Teu statistics (container counts). Retrieved from http://www.portoflosangeles.org/maritime/stats.asp

Slooten, E., & Dawson, S. M. (2008). Sustainable levels of human impact for hector’s dolphin. The Open Conservation Biology Journal, 2, 37-43. Retrieved from http://www.benthamscience.com/open/toconsbj/articles/V002/37TOCONSBJ.pdf

Tyack, P. (1986). Population biology, social behavior and communication in whales and dolphins. Trends in Ecology and Evolution, 1(6), 144-150. Retrieved from http://www.sciencedirect.com.libproxy.usc.edu/science/article/pii/016953478690042X


0 views

© 2019 Richelle Tanner

  • Twitter Clean
  • facebook