Daniel Pugh
2/28/15
Writing 100
Alex Block
Causation Stage, Draft 1
The longfin smelt is a key species, which is affected by the relationship with
humans and their needs for the Sacramento San-Joaquin Delta, and the stress that it
places on the longfin smelt’s living habitat. The longfin smelt or better known as
pirinchus thaleichthys, “is an anadromous smelt (family Osmeridae) found in California’s
bay, estuary, and nearshore coastal environments from San Francisco Bay north to Lake
Earl, near the Oregon border. The San Francisco Estuary and the Sacramento-San
Joaquin Delta supports the largest longfin smelt population in California, and Humboldt
Bay likely ranks second in longfin smelt abundance.”(www.dfg.ca.gov/habcon/cesa) The
longfin smelt has a very short lifespan, living max of usually three years. Most of this
species reach maturity at two years of age and their size ranges from 120 mm to 140 mm
in length, which is standard length for this species of smelt. The adult smelts of this
species spend their adult lives in bays, estuaries, and coastal areas that are near the
shores. They then migrate to freshwater areas in order to spawn and reproduce more
offspring. Adult longfin smelt migrate to freshwater areas and, “Adult longfin smelt
migrate into low salinity or freshwater reaches of coastal rivers and tributary streams to
spawn. Newly hatched larvae are 5 mm to 8 mm long.”(www.dfg.ca.gov/habcon/cesa)
these larvae are then able to swim upstream to the areas necessary for them to grow and
continue the lifecycle of this particular species, the longfin smelt. The longfin smelt’s
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natural habitat is centered on estuaries, saltwater and freshwater areas, and areas with
middle to deeper areas of water. The longfin smelt’s purpose in the food chain is to
regulate the population of smaller organisms such as opossum shrimp (also known as
Mysis relicta). Without the longfin smelt the shrimp becomes overpopulating resulting in
a disruption of the food chain eliminating the longfin smelt as a regulator of the opossum
shrimp and also as being prey for the other predators which depend on the longfin smelt
for their source of food. Therefore, with the longfin smelt inhabiting the delta itself, there
are certain needs that the fish itself need in order to survive and keep the food chain in the
delta balanced.
The longfin smelt is a crucial species in the delta, and it has needs that make it
possible for it to be able to live and thrive successfully. The species itself encounters
many different living conditions like water temperatures and salinities (freshwater to
saltwater) while they proceed through their life cycles and they are rarely found in water
temperatures that exceed 22 degrees Celsius. They are mostly found in the middle water
areas and lower on towards the bottom and are known to migrate up and down the water
column following prey at night. These conditions are low salinity areas/freshwater areas,
areas where the elevation of the water is very deep, seeing as how they occupy only the
mid-to-bottom level of the areas, which they inhabit. The older adult longfin smelts
prefer areas of salinity recorded at 15 to 30 parts per thousand. They also require
freshwater predominantly in order to spawn and survive. These conditions are vital in
order for the species to survive as illustrated by the quote, “Freshwater flow in the Delta
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during incubation and the larval rearing period is a strong correlate of longfin smelt
abundance, likely because high flow increases the volume of brackish water preferred by
larval and juvenile smelt (Baxter et al. 2010).” These water elevations are necessary
because it is how they swim up and down the streams in order to follow their prey at
night. Turbidity is also a key player in the advancement and growth of the smelt as
illustrated here in comparison showing the effects that turbidity has on the smelt’s
population and growth rate, “Smelt are found at higher densities in turbid water, although
there is some evidence that turbidity may negatively affect growth and condition. In
Suisun Bay, comparison of longfin smelt in the shallow, less turbid northern channel
versus the deep, more turbid southern channel revealed greater abundance in the southern
channel, but also lower feeding and growth rates (Hobbs 2009)” This shows that with the
turbid water there is a greater growth and feeding rate as opposed to if there is just is less
turbid water and thus reducing the growth and feeding rate. Just as the longfin smelt
depends on the Sacramento San-Joaquin Delta to provide it with a stabilized environment
and necessary resources to thrive and maintain its species, humans also depend on the
delta a great deal in order to satisfy as well as sustain our cultural, rural, and agricultural
needs.
As the Sacramento San-Joaquin delta plays a key part in our daily lives as human
beings it helps to service majority of Californians with the resource that is most valuable
to our well being, water. “The Delta is often considered the nexus of California's
statewide water system. About half the total river flow in the state passes through this
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region, from which water is exported to the San Joaquin Valley, Southern California and
portions of the Bay area to supply some 1,130,000 acres (460,000 ha) of farmland and 23
million people in central and Southern California.” with the vast majority of those acres
being agricultural and rural, it goes to show the large and devastating impact the delta has
on us and the conflict that may arise since we pull on the delta itself. “The Delta provides
an estimated 7 million acre feet (8.6 km3) of water per year, of which about 100,000 acre
feet (0.12 km3) are exported to the San Francisco Bay Area, 1.7 million acre feet
(2.1 km3) are used locally, and over 5 million acre feet (6.2 km3) are exported to the San
Joaquin Valley, coastal Central and Southern California”("Delta Fact Sheet". U.S.
Geological Survey. 2000. Retrieved 2013-08-15.) The Sacramento San-Joaquin delta
helps, “locally the Delta provides water for cities and towns in five counties and for over
1,800 agricultural users.”("Where Rivers Meet-The Sacramento-San Joaquin Delta".
State Water Project. California Department of Water Resources. 2008-07-18. Retrieved
2013-08-15.) This illustrates that the delta itself plays a key part in servicing a large area
of rural areas. “The Contra Costa Canal and North Bay Aqueduct also take Delta water,
supplying the nearby San Francisco Bay Area. Locally, the Delta provides water for cities
and towns in five counties and for over 1,800 agricultural users” ("Where Rivers MeetThe Sacramento-San Joaquin Delta". State Water Project. California Department of
Water Resources. 2008-07-18. Retrieved 2013-08-15.), thus, not only with just our
agriculture and rural needs the delta helps to service a large area of California itself. The
delta then helps to provide water and irrigation to the agricultural side of California,
which is, a big part of our daily lives as Californians. The “The Delta produces crops
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valued at about $500 million annually, making it one of the most productive farming
regions of the United States in terms of crop value per unit area. Agriculture provides
secondary benefits of over $2 billion to the local economy. Major crops grown in the
Delta include corn, grain, hay, sugar beets, alfalfa, tomatoes, asparagus, and safflower;
various fruits are also raised here, as well as some livestock.”("Where Rivers Meet-The
Sacramento-San Joaquin Delta". State Water Project. California Department of Water
Resources. 2008-07-18. Retrieved 2013-08-15), with this showing the very obvious need
that California has for the dependency on the Delta itself for not only rural needs but also
agricultural needs, this also presents us with the conflict between the humans needs and
the longfin smelt’s needs.
The problem for the longfin smelt is the affected living conditions, which have
been altered by humans constantly pulling on the delta to supply our many irrigational as
well as recreational needs. The longfin smelt needs certain living conditions in order to
thrive, reproduce, and effectively contribute to the food chain to help prevent the
overpopulation of its prey the opossum shrimp. With the delta being a large contributor to
what Californians do every day as well as a big contributor to the success of agriculture
here in California but also the import and export of agricultural goods out to other places
around the world, the delta has been stressed and the population of longfin smelt has
experienced a decrease as well. Longfin smelt require certain conditions to live
peacefully and humans require a certain amount of water to do our agricultural duties
(farmers) and daily activities (Californians). Longfin smelts need a certain level of
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salinity in order to be able to reproduce successfully. Adult smelts look to migrate to
waters with salinity levels between sixteen and eighteen degrees Celsius in order to
spawn and continue to make more offspring. The water levels themselves have been
affected with most of the delta islands within the delta itself being reduced to ten to
twenty-five feet below sea level. Therefore, telling us that as we continue to pull out
more and more water to irrigate the crops or to supply us with drinking water that the
water levels are slowly being reduced thus, reducing the depth that the longfin smelt has
to live in. The longfin smelt was once one of the most abundant fish in the delta.
Californians have reduced low delta outflow, which in turn has affected the smelt
dramatically. Other key factors, which have caused conflict due to human interference,
are, “Water diversions by the State Water Project (SWP) and Central Valley Project
(CVP) have contributed to lower Delta outflow. Such diversions also pose a threat to
longfin smelt because of their potential to entrain longfin smelt, particularly larvae and
juveniles, in pumping stations (Kimmerer and Nobriga 2008). Risk of entrainment was
fairly constant over the last 50 to 100 years until the SWP and CVP increased diversions
and potential for entrainment (Moyle 2002).” and these have reduced the amount of water
going out and affecting the living patterns of the smelt. The introduction of predators by
us have helped to reduce the population of longfin smelt as well illustrated by this
particular quote, “The introduction of the overbite clam, Corbula amurensis, in the late
1980s changed the benthic community and is likely responsible for the observed stepdecline in mysid shrimp, which are an important prey item for longfin smelt. The
introduction of non-native copepods may have further reduced the quality of prey
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available (Baxter et al. 2010). While introduced predators such as striped bass do not
appear to be a threat to adult longfin smelt (Baxter 2009), egg and larval predators such
as the Mississippi silverside (Menidia audens) may pose a threat (Moyle 2002). “, with
the introduction of certain predators to prey on the prey that is the primary source for the
longfin smelt, the population has been critically affected as it looks for scarce resources
considering, its number one resource for food has become prey to another consumer.
With these issues however, there arises some questions that are presented with every
argument that can be made in relationship to whether or not the longfin smelt is worth
saving.
The questions that have arisen in response to this critical issue are many that
propose many different angles on how the endangering of the longfin smelt should be
handled. Many will propose the question of, “Well why is the longfin smelt just as
important as preserving water so that I can have the necessary resource to give to my
family?” Others will argue on the subject matter that the longfin smelt did nothing to
deserve its population and habitat being reduced at an alarming rate and that we need to
look into alternative solutions in order to better preserve the species which has become
classified as endangered. The other questions that have come about is the one that asks,
“What efforts do we make in order to reduce our intake of the Sacramento San-Joaquin
delta and also what other sort of conservation efforts or alternatives do we need to look
into in order to lessen the strain that we are placing on the delta and the species within
them especially the longfin smelt delta?”