No Fish Too Small: The Role of the Delta Smelt as an Ecological Indicator in the California Bay-

Delta

Mike StoeverStrategies in Watershed Management

Johns Hopkins University

Overview of the issue• The Delta smelt, a federally endangered fish species endemic

to the California Bay-Delta region in the central part of the state, is at risk of becoming extinct

• In order to prevent this from occurring, dramatic reductions in the freshwater allocated to central and southern California from the Bay-Delta and San Francisco estuary have been enacted

• This has resulted in unhappy agricultural and downstream users who value their water allotment above a single species of fish

• Correspondingly, this has left conservationists and those tasked with ensuring Endangered Species Act compliance (along with the overall health of the ecosystem) fighting to protect the species and explain its importance to all stakeholders.

Background on Delta smelt • Found only in California’s Sacramento-San Joaquin

estuary, this species typically grows to 2.4-2.8 inches in length

• Has a low level of reproduction and only a one-year lifespan, yet serves as a vital food source for many animal species in the region

• While a saltwater tolerant species, it is rarely found where seawater makes up more than 1/3 of the total water, preferring the freshwater side of the mixing zone (where fresh and saltwater meet)

• As water demand downstream increases, this mixing zone is drawn upstream and into river channels, reducing suitable habitat for the species (whose eggs are reliant upon stable surfaces, which river channel bottoms most certainly are not) and making them more susceptible to diversions

Historic Delta smelt habitat

Major threats facing the Delta smelt• Changes and fluctuations in the mixing zones where the species

makes its home, often via reductions in outflows and losses due to diversions and entrainments

• Hybridization through mating with competitors, producing sterile offspring and a loss of important genetic information

• Water pollution negatively impacting habitat• Combined with the current drought, these threats have caused a

massive decline in the number of Delta smelt found in the region, as evidenced by the figure below

Competing water concerns • 70% of California’s water originates in the north,

while 70% percent of the demand is in the south

Sacramento

Competing water concerns, cont.

• The flow of this water, which is often diverted from above Delta smelt habitat, ensures adequate and efficient downstream flows for the two-thirds of the state’s residents and three million acres of crops who depend upon it

• As noted earlier, these diversions have resulted in major reductions of Delta smelt habitat and in their population, which is scattered in such small numbers that scientists fear the species can no longer reproduce

Tensions between users• The Delta smelt’s status as a

federal (and state) threatened species forces state officials to reduce downstream deliveries of water when the pumps that do so harm the fish, or when its habitat becomes too salty

• The effects of this process can be seen on the right-hand side of this slide

Tensions between users, cont.

• However, when the state declares emergency waivers, which it has done in recent years due to the drought, it is allowed to ignore minimum flow requirements and is able to continue exporting water

• This has created tensions between environmentalists and downstream users, resulting in lawsuits which have, so far, been decided in favor of the fish and its habitat

Why should you care? The role of the Delta smelt as ecological indicator

• This tiny fish is actually one of the best indicators of environmental conditions in the Bay-Delta; if they are alive and well, other fish, birds, mammals, and plants will also thrive

• It is a crucial link in the food web of the ecosystem; if one link in the chain gets broken, other species’ populations may decline along with it

• Thus, its decline is a warning that other native Delta fish species who have also fallen to alarmingly low levels may be lost as well

Additional species impacted

• The species that rely upon the Delta smelt as part of their food chain are myriad, and they include:

Longfin smelt Chinook salmon Sturgeon

• Also, there is the potential for the loss of Delta smelt to reach the orca whale population that lives just off the coast of the San Francisco Bay Area, as they rely upon yearly salmon runs (that in turn rely upon sufficient quantities of smelts) for their survival

Potential solutions • While water diversions and past management strategies have been

the leading cause of the decline in Delta smelt, the recent drought has truly exacerbated the issue

• Thus, one of the best solutions to save the smelt is through better water management for continuous dry years, along with a reassessment of currently over-allocated water

• Proactive management strategies need to be enacted to prevent other fish and animal species from facing fates similar to the smelt, strategies that require learning more about their requirements and managing parts of the ecosystem specifically for their benefit

• Finally, a water use balance must be struck and its consequences truly accepted, as both human and wildlife populations rely on the same limited water supplies

Thank you!

- For additional information, please refer to the sources found in the notes sections of this presentation