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US Fish & Wildlife Service FieldNotes

STOCKTON FWO: Liberty Island Sampling Season is Teeming with Possibilities in Determining What Fish are Colonizing This Wetland Habitat

Region 8, February 1, 2011
Crystal Castle of the Delta Juvenile Fish Monitoring Program identifying larval fish in the lab.
Crystal Castle of the Delta Juvenile Fish Monitoring Program identifying larval fish in the lab. - Photo Credit: n/a
Denise Barnard and Amber Aguilera of the Delta Juvenile Fish Monitoring Program collecting and preserving samples in the field.
Denise Barnard and Amber Aguilera of the Delta Juvenile Fish Monitoring Program collecting and preserving samples in the field. - Photo Credit: n/a

By Kate Erly, Stockton FWO

 

Adult and juvenile fish identification can be a hard task with so many different species swimming the Delta. Now, shrink those fish down to 4mm, die them pink and preserve them in formalin. Carefully skilled staff of the Stockton Fish and Wildlife Office’s Delta Juvenile Fish Monitoring Program (DJFMP) have spent hours in the lab pouring over microscopes in order to learn what is inhabiting Liberty Island, a restoring freshwater wetland.

The DJFMP has been hard at work reenergizing a special study originally started in 2003-2004 focusing on larval fishes who now call Liberty Island their home. Liberty Island is located in the San Joaquin-Sacramento Delta, crossing into Yolo and Solano Counties.

In 1998, Liberty Island, a once flourishing farmland subject to frequent flooding from levee breaks, began its transformation back to a tidally-influenced freshwater marsh when levee’s breached for the last time and were not repaired. However, after just over a decade the island appears to be teeming with both vegetation and aquatic life.

Starting in January 2011, the planning process took place as to the most effective manner in which to execute the DJFMP’s Liberty Island goal; to determine what fish are colonizing this restoring wetland habitat.

From February through September 2011, crews ventured out to Liberty Island to sample larval fishes. Once a week, skillfully maneuvering 18-foot aluminum boats through the Delta system, Service staff made their way out to the north or south end of the island to conduct several surface trawls and collect environmental data. Once samples were back on dry land, the real fun began. Samples brought back to the lab were rinsed of chemicals and all fish were extracted and identified down to species using physical characteristics and dichotomous keys.

Excited that our field season is coming to a close, we now can begin the process of interpreting the data. Will we find that this now submerged island complete with telephone poles and a road is now a safe haven for the native splittail, Pogonichthys macrolepidotus, delta smelt, Hypomesus transpacificus, and longfin smelt, Spirinchus thaleichthys? Will we find a correlation between our ongoing Liberty Island beach seine juvenile fish collections and our larval collections? Whatever our data may show, we are already eagerly looking forward to the 2012 sampling season where we anticipate expanding our current sampling methodology as well as adding a zooplankton component to the project.

Contact Info: Joseph Kirsch, 209-334-2968 ext. 309, joseph_kirsch@fws.gov