Early Life History of Fishes in the San Francisco Estuary and Watershed

2004 ◽  
Keyword(s):  
San Francisco ◽  
Open Water ◽  
Early Life History ◽  
Spatial And Temporal Variability ◽  
Larval Rearing ◽  
Restored Wetlands ◽  
Marsh Edge ◽  
Reference Marsh ◽  
History Of ◽  
Native Fishes

<em>Abstract.</em>—We examined the spatial and temporal variability of native and alien ichthyoplankton in three habitat types (marsh edge, shallow open-water, and river channel) in one reference and three restored marshes in the Sacramento–San Joaquin Delta, California, during 1998 and 1999. More than 6,700 fish embryos and 25,000 larvae represented by 10 families were collected in 240 tows during the 2-year study. Overall, the assemblage was dominated by alien fishes, but natives were more abundant during winter and spring, whereas aliens were more abundant during summer. Overall abundance was highest in marsh edge habitats, suggesting that this habitat provides favorable larval rearing habitats for many fishes. The reference marsh was dominated by alien species making it difficult to assess whether it had attributes that promoted use by native fish. Ichthyoplankton abundance varied comparably at restored sites of similar configuration. The restored site, with minimal tidal exchange and greater lower trophic productivity, supported the highest densities of alien fish. We conclude that restoration projects in this region of the estuary must consider the potential impacts of alien fishes on natives and evaluate strategies designed to improve recruitment success of native fishes. Specifically, we suggest that restored wetlands that offer only winter and spring inundation periods may provide maximum benefits to natives while limiting access by many alien fishes regardless of specific habitat-use requirements.

Early Life History of Fishes in the San Francisco Estuary and Watershed

2004 ◽  
Keyword(s):  
Growth Rate ◽  
San Francisco ◽  
Striped Bass ◽  
Growth Rates ◽  
Early Life History ◽  
San Francisco Estuary ◽  
Annual Growth ◽  
Factors Affecting ◽  
Juvenile Abundance ◽  
History Of

<em>Abstract.</em>—We investigated factors affecting growth of larval striped bass <em>Morone saxatilis </em>in the San Francisco Estuary from 1984 to 1993. We estimated ages and growth rates of larval striped bass from daily otolith increments. Mean annual growth rates of 6–14 mm standard length striped bass varied from 0.13 to 0.27mm/d, the lowest rate occurring in 1989 and the highest in 1992. The 1989 growth rate was significantly lower than all other years, and growth rates for 1992 and 1993 were significantly higher than all other years, but did not differ from one another. Differences in annual growth rates apparently were due mainly to differences in mean annual prey densities because growth rate increased as prey density increased. Compared to both laboratory measured growth rates and growth rates of field-caught Chesapeake Bay larvae, growth rates from the San Francisco Estuary appeared to be high for the food available, indicating that larvae can grow at relatively high rates even at low prey densities. Correlation analyses did not support density-dependent control of growth rates. Growth rate was not significantly related to mean annual conductivity, water temperature, mortality rates, or the juvenile abundance index, but was significantly and positively correlated with densities of 1-mm length-groups of 9–14-mm striped bass.

Early Life History of Fishes in the San Francisco Estuary and Watershed

2004 ◽  
Keyword(s):  
San Francisco ◽  
Striped Bass ◽  
Vertical Migration ◽  
Early Life ◽  
Life Histories ◽  
Early Life History ◽  
Small Surface ◽  
Delta Smelt ◽  
Larval Fishes ◽  
History Of

<em>Abstract.</em>—The goal of this study was to determine if the vertical distribution of larval delta smelt <em>Hypomesus transpacificus </em>and striped bass <em>Morone saxatilis </em>was affected by tidal stage and diel period. Delta smelt and striped bass have similar early life histories in that their larvae drift downstream from freshwater spawning habitats to brackish water rearing habitats. Little is known on whether the larvae undergo a vertical migration as they move downstream. Conical plankton nets were used to collect larval fishes from the surface, middle, and bottom sections of the main channels of the Sacramento and San Joaquin rivers. Samples were collected over six paired day–night cruises. Approximately 45,000 fish were collected; 82% were striped bass and 2% were delta smelt. More delta smelt were caught at night than during the day, and more at middle depth than surface or bottom. Very few striped bass were found at surface during day; most were caught at middle depth. Both species were fairly dispersed throughout the water column at night. Although striped bass larvae appear to undergo a small surface to middepth migration, this study indicates that larval delta smelt and striped bass do not undergo a mass diel or tidal vertical migration as they drift down the Sacramento and San Joaquin rivers.

Early Life History of Fishes in the San Francisco Estuary and Watershed

2004 ◽  
Keyword(s):  
San Francisco ◽  
Sublethal Effects ◽  
Total Mortality ◽  
Early Life History ◽  
Toxicity Tests ◽  
Metabolic Dysfunction ◽  
Exposed Fish ◽  
Pogonichthys Macrolepidotus ◽  
History Of ◽  
Acute Toxicity Tests

<em>Abstract.</em>—Runoff from dormant spray applications to orchards can contain the insecticides diazinon and esfenvalerate, which may affect the health of the threatened splittail <em>Pogonichthys macrolepidotus</em>. To examine the potential effects of these two insecticides, splittail larvae were exposed to diazinon, esfenvalerate, and a mixture of the two insecticides in static renewal 96-h acute toxicity tests. Surviving fish were transferred to clean water for an additional 14 d (18 d total). Mortality, morphological anomalies, histopathology, and growth determinations were made to assess lethal and sublethal effects. The combination of diazinon and esfenvalerate produced less than additive (independent) toxicity. Diazinon (singly and in combination with esfenvalerate) produced latent toxicity after the 96-h exposure, as demonstrated by reduced growth and increased spinal deformities. Metabolic dysfunction in the liver and inflammation of the pancreas were likely related to slower growth of diazinon-exposed fish. These symptoms were almost absent from esfenvalerate-exposed fish. The use of 14-d EC50 values and the measurement of biomarkers may more accurately describe the effects of 96-h shortterm exposure to these insecticides than traditional 96-h LC50 values.

Early Life History of Fishes in the San Francisco Estuary and Watershed

2004 ◽  
Keyword(s):  
San Francisco ◽  
Fish Larvae ◽  
Light Trap ◽  
Early Life History ◽  
Light Sources ◽  
Light Traps ◽  
Natural Stream ◽  
History Of ◽  
Distribution And Ecology ◽  
Different Color

<em>Abstract.</em>—Light traps have been used to study the distribution and ecology of fish larvae in a variety of waters. Yet the physical and taxonomic limitations of light traps have been little studied, particularly in lotic systems. The purpose of this study was to examine aspects of light trap use, bias, and specificity in a natural stream setting. We sampled fish larvae using light traps in the upper Sacramento River watershed in April (2001, 2002) and June (2002) using five different color light sources and two trap sizes. Our results suggest that (1) small traps are as effective at sampling fish larvae as large traps, (2) color of light and/or relative intensity of light have strong effects on numbers of larvae collected, and (3) environmental factors play a role in the number of larvae collected over short time periods.

Early Life History of Fishes in the San Francisco Estuary and Watershed

2004 ◽  
Keyword(s):  
San Francisco ◽  
Early Life History ◽  
Swim Bladder ◽  
Delta Smelt ◽  
Vitro Fertilization ◽  
Total Length ◽  
History Of ◽  
Newly Hatched Larvae ◽  
Swim Bladder Inflation

<em>Abstract.</em>—Delta smelt <em>Hypomesus transpacificus </em>juveniles caught in the Sacramento–San Joaquin Delta were reared in the laboratory to full sexual maturity, and embryos were obtained by in vitro fertilization and natural spawning in tanks. Duration of embryo development to hatching was 11–13 d at 14.8–16.0°C, with a development rate similar to other <em>Hypomesus</em>. Newly hatched larvae were 5.1–5.7 mm total length and resorbed the yolk sac within 6 d and lipid globule within 10 d. Exogenous feeding on rotifers started 5–6 d posthatch. Delta smelt have indirect development with a prolonged larval phase prior to juvenile metamorphosis. Fin differentiation began at 10–12 mm, 20–30 d posthatch, and was completed at 19–20 mm and 50–60 d, concomitant with swim bladder inflation. Metamorphosis was completed in 120 d when juveniles were about 35 mm total length. The prolonged larva fin fold stage lacking a functional swim bladder may be an adaptation to passively use water currents in estuarine nursery areas.

Early Life History of Fishes in the San Francisco Estuary and Watershed

2004 ◽  
Keyword(s):  
San Francisco ◽  
Native Species ◽  
Larval Fish ◽  
Micropterus Salmoides ◽  
Early Life History ◽  
Drainage Water ◽  
Early Spring ◽  
Larval Fishes ◽  
Pogonichthys Macrolepidotus ◽  
History Of

<em>Abstract.</em>—We sampled larval fish in 1999 and 2001 on a restored floodplain along the lower Cosumnes River, California, from the onset of flooding to when the sites dried or when larval fish became rare. We collected more than 13,000 fish, of which prickly sculpin <em>Cottus asper </em>made up the majority (73%). Eleven species made up 99% of the catch. Three native fishes (prickly sculpin, Sacramento sucker <em>Catostomus occidentalis</em>, and splittail <em>Pogonichthys macrolepidotus</em>) and two alien species (common carp <em>Cyprinus carpio </em>and bigscale logperch <em>Percina macrolepida</em>) were associated with higher inundation and cool temperatures of early spring. In contrast, five alien taxa, sunfish <em>Lepomis </em>spp., largemouth bass <em>Micropterus salmoides</em>, crappie <em>Pomoxis </em>spp., golden shiner <em>Notemigonus crysoleucas</em>, and inland silverside <em>Menidia beryllina</em>, were associated with less inundation and warmer water temperatures. One native species, Sacramento blackfish <em>Orthodon microlepidotus</em>, was also associated with these conditions. Species did not show strong associations with habitat because of different spawning times of adults and expansion and contraction of flood waters. Most species could be found at all sites throughout flooded habitat, although river and floodplain spawning fishes usually dominated sites closest to levee breaches. Highest species richness was consistently found in two sloughs with permanent water because they both received drainage water from the floodplain and had a complement of resident species. Splittail, a floodplain spawner, was found primarily in association with submerged annual plants. Our results suggest that a natural hydrologic cycle in spring is important for providing flooding and cool temperatures important for many native larval fishes. Alien fishes are favored if low flows and higher temperatures prevail. Restoration of native fish populations that use floodplains for rearing should emphasize early (February–April) flooding followed by rapid draining to prevent alien fishes from becoming abundant.

Early Life History of Fishes in the San Francisco Estuary and Watershed

2004 ◽  
Keyword(s):  
Life History ◽  
San Francisco ◽  
Striped Bass ◽  
Early Life ◽  
Early Life History ◽  
San Francisco Estuary ◽  
Delta Smelt ◽  
History Of ◽  
Acanthogobius Flavimanus ◽  
Longfin Smelt

<em>Abstract.</em>—We analyzed data on spring and summertime larval and juvenile fish distribution and abundance in the upper San Francisco Estuary (SFE), California between 1995 and 2001. The upper SFE includes the tidal freshwater areas of the Sacramento–San Joaquin Delta downstream to the euryhaline environment of San Pablo Bay. The sampling period included years with a variety of outflow conditions. Fifty taxa were collected using a larval tow net. Two common native species, delta smelt <em>Hypomesus transpacificus </em>and longfin smelt <em>Spirinchus thaleichthys</em>, and four common alien taxa, striped bass <em>Morone saxatilis</em>, threadfin shad <em>Dorosoma petenense</em>, gobies of the genus <em>Tridentiger</em>, and yellowfin goby <em>Acanthogobius flavimanus</em>, were selected for detailed analysis. Outflow conditions had a strong influence on the geographic distribution of most of the species, but distribution with respect to the 2 psu isohaline (X2) was not affected. The distribution patterns of delta smelt, longfin smelt, and striped bass were consistent with larvae moving from upstream freshwater spawning areas to downstream estuarine rearing areas. There were no obvious relationships of outflow with annual abundance indices. Our results support the idea of using X2 as an organizing principle in understanding the ecology of larval fishes in the upper SFE. Additional years of sampling will likely lead to additional insights into the early life history of upper SFE fishes.

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