Old School vs. New School: Status of Threadfin Shad (<em>Dorosoma petenense</em>) Five Decades After Its Introduction to the Sacramento–San Joaquin Delta
<p>Threadfin shad (<em>Dorosoma petenense</em>) is a schooling pelagic forage fish native to watersheds of the Gulf Coast of North America. Around 1962 it invaded the Sacramento-San Joaquin Delta from upstream reservoirs, where it was stocked to support sport fisheries. It quickly...
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| Format: | Article |
| Language: | English |
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eScholarship Publishing, University of California
2009-09-01
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| Series: | San Francisco Estuary and Watershed Science |
| Subjects: | |
| Online Access: | http://escholarship.org/uc/item/4dt6p4bv |
| _version_ | 1828453078791094272 |
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| author | Frederick Feyrer Ted Sommer Steven B. Slater |
| author_facet | Frederick Feyrer Ted Sommer Steven B. Slater |
| author_sort | Frederick Feyrer |
| collection | DOAJ |
| description | <p>Threadfin shad (<em>Dorosoma petenense</em>) is a schooling pelagic forage fish native to watersheds of the Gulf Coast of North America. Around 1962 it invaded the Sacramento-San Joaquin Delta from upstream reservoirs, where it was stocked to support sport fisheries. It quickly became, and continues to be, one of the most abundant fishes collected by ongoing monitoring programs in the delta. A substantial portion of the delta provides suitable abiotic habitat and so the species is widely distributed. However, in routine sampling it is most commonly collected and most abundant in the southeastern delta, where suitable abiotic habitat (relatively deep, clear water with low flow) coincides with high prey abundance. Apparent growth rate appears to be relatively fast with summer-spawned age-0 fish attaining fork lengths of 70 to 90 mm by the onset of winter. During fall months (September through December) apparent growth rate of age-0 fish has exhibited no long-term trend but has been negatively related to abundance, suggesting that density-dependent factors may be important to the population. Although abundance has fluctuated since its introduction almost five decades ago, it has recently dropped to persistent near-record lows since 2002, which has been coincident with similar declines for other pelagic species in the delta. The recent decline is apparent in two long-term monitoring programs, fish salvaged from the diversions of the state and federal water projects, and commercial fishing harvest. It appears that the decline is, at least in part, a function of fewer and smaller schools of threadfin shad encountered relative to the past. There was little evidence from the data examined for consistent stock-recruit or stage-recruit effects on the population. It is likely that a combination of abiotic and biotic factors regionally-focused where threadfin shad are most abundant, which may sometimes be episodic in nature, have a large effect on abundance. Focused studies and sampling of threadfin shad are lacking but are necessary in order to better understand population dynamics in the delta.</p> |
| first_indexed | 2024-12-11T00:02:11Z |
| format | Article |
| id | doaj.art-665c920f3a674b50ba0422c5239be915 |
| institution | Directory Open Access Journal |
| issn | 1546-2366 |
| language | English |
| last_indexed | 2024-12-11T00:02:11Z |
| publishDate | 2009-09-01 |
| publisher | eScholarship Publishing, University of California |
| record_format | Article |
| series | San Francisco Estuary and Watershed Science |
| spelling | doaj.art-665c920f3a674b50ba0422c5239be9152022-12-22T01:28:26ZengeScholarship Publishing, University of CaliforniaSan Francisco Estuary and Watershed Science1546-23662009-09-0171ark:13030/qt4dt6p4bvOld School vs. New School: Status of Threadfin Shad (<em>Dorosoma petenense</em>) Five Decades After Its Introduction to the Sacramento–San Joaquin DeltaFrederick Feyrer0Ted Sommer1Steven B. Slater2Applied Science Branch, U.S. Bureau of ReclamationAquatic Ecology Section, California Department of Water ResourcesLong-Term Monitoring Unit, California Department of Fish and Game<p>Threadfin shad (<em>Dorosoma petenense</em>) is a schooling pelagic forage fish native to watersheds of the Gulf Coast of North America. Around 1962 it invaded the Sacramento-San Joaquin Delta from upstream reservoirs, where it was stocked to support sport fisheries. It quickly became, and continues to be, one of the most abundant fishes collected by ongoing monitoring programs in the delta. A substantial portion of the delta provides suitable abiotic habitat and so the species is widely distributed. However, in routine sampling it is most commonly collected and most abundant in the southeastern delta, where suitable abiotic habitat (relatively deep, clear water with low flow) coincides with high prey abundance. Apparent growth rate appears to be relatively fast with summer-spawned age-0 fish attaining fork lengths of 70 to 90 mm by the onset of winter. During fall months (September through December) apparent growth rate of age-0 fish has exhibited no long-term trend but has been negatively related to abundance, suggesting that density-dependent factors may be important to the population. Although abundance has fluctuated since its introduction almost five decades ago, it has recently dropped to persistent near-record lows since 2002, which has been coincident with similar declines for other pelagic species in the delta. The recent decline is apparent in two long-term monitoring programs, fish salvaged from the diversions of the state and federal water projects, and commercial fishing harvest. It appears that the decline is, at least in part, a function of fewer and smaller schools of threadfin shad encountered relative to the past. There was little evidence from the data examined for consistent stock-recruit or stage-recruit effects on the population. It is likely that a combination of abiotic and biotic factors regionally-focused where threadfin shad are most abundant, which may sometimes be episodic in nature, have a large effect on abundance. Focused studies and sampling of threadfin shad are lacking but are necessary in order to better understand population dynamics in the delta.</p>http://escholarship.org/uc/item/4dt6p4bvDorosoma petenensebaitfishclupeidaeSan Francisco Estuarypelagic organism decline |
| spellingShingle | Frederick Feyrer Ted Sommer Steven B. Slater Old School vs. New School: Status of Threadfin Shad (<em>Dorosoma petenense</em>) Five Decades After Its Introduction to the Sacramento–San Joaquin Delta San Francisco Estuary and Watershed Science Dorosoma petenense baitfish clupeidae San Francisco Estuary pelagic organism decline |
| title | Old School vs. New School: Status of Threadfin Shad (<em>Dorosoma petenense</em>) Five Decades After Its Introduction to the Sacramento–San Joaquin Delta |
| title_full | Old School vs. New School: Status of Threadfin Shad (<em>Dorosoma petenense</em>) Five Decades After Its Introduction to the Sacramento–San Joaquin Delta |
| title_fullStr | Old School vs. New School: Status of Threadfin Shad (<em>Dorosoma petenense</em>) Five Decades After Its Introduction to the Sacramento–San Joaquin Delta |
| title_full_unstemmed | Old School vs. New School: Status of Threadfin Shad (<em>Dorosoma petenense</em>) Five Decades After Its Introduction to the Sacramento–San Joaquin Delta |
| title_short | Old School vs. New School: Status of Threadfin Shad (<em>Dorosoma petenense</em>) Five Decades After Its Introduction to the Sacramento–San Joaquin Delta |
| title_sort | old school vs new school status of threadfin shad em dorosoma petenense em five decades after its introduction to the sacramento san joaquin delta |
| topic | Dorosoma petenense baitfish clupeidae San Francisco Estuary pelagic organism decline |
| url | http://escholarship.org/uc/item/4dt6p4bv |
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