Biology and Population Dynamics of Sacramento Splittail (Pogonichthys macrolepidotus) in the San Francisco Estuary: A Review
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Abstract:
The Sacramento splittail (Pogonichthys macrolepidotus) is a cyprinid fish endemic to the Central Valley of California with a range that centers on the San Francisco Estuary. It is a state Species of Special Concern and was only recently (2003) delisted as a threatened species by the U. S. Fish and Wildlife Service. Splittail live 7-9 years, tolerate a wide range of environmental conditions, and have high fecundity. Typically, adults migrate upstream in January and February and spawn on seasonally inundated floodplains in March and April. In May the juveniles migrate back downstream to shallow, brackish water rearing grounds, where they feed on detritus and invertebrates for 1-2 years before migrating back upstream to spawn. Seven long-term sampling programs in the estuary indicate that the splittail population is maintained by strong year classes resulting from successful spawning in wet years, although some spawning occurs in all years. Modeling shows them to be resilient, but managing floodplains to promote frequent successful spawning is needed to keep them abundant. Additionally, it is important to provide safe migration corridors between spawning and rearing grounds as well as abundant high-quality brackish water rearing habitat. Key research needs are (1) to examine how the timing, magnitude, and duration of high flows contribute to the generation of strong year classes, (2) to describe differences in young of year survival on the floodplain and in river margins from hatching to down-river migration, (3) explore the possible trophic effects of new invaders such as the overbite clam and Siberian prawn, and (4) determine the response of splittail populations to climate change and sea level rise.Keywords:
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Fresh water
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Three arctic charr (Salvelinus alpinus) morphs coexist within the Dieset watercourse (79°10'N, 11°20'E) on Spitsbergen, Svalbard. Small freshwater resident charr exhibited a very slow growth rate, while large freshwater resident charr grew at a rate comparable to that reported for cannibalistic charr elsewhere. First-time sea migrants of the anadromous charr were similar in size to their more southern-living Norwegian conspecifics, but on average two years older. The average number of sea runs before first-time spawning was 3.6 for males and 4.4 for females. Veteran migrants displayed growth comparable to that of anadromous charr from more southern populations. In all three morphs, sex ratio did not differ from unity. The short-lived small residents matured from an age of 4 years, 3 to 4 years earlier than did large residents and anadromous charr. The majority of small resident and anadromous charr spawn a maximum of three times, while large resident charr may spawn up to seven times. Although 69% of large resident charr were older than 15 years, only 5.7% of reproductive anadromous charr exceeded this age. This divergence may indicate different reproductive strategies between the two morphs. There was no evidence of reproductive isolation between these High Arctic charr morphs.
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Arctic char
Norwegian
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Smelt
Semelparity and iteroparity
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Juvenile freshwater and anadromous inconnu Stenodus leucichthys regulated plasma ions following a direct transfer from fresh to brackish water (10–15‰), but suffered osmoregulatory collapse with 100% mortality in 48 h when directly transferred to 25‰ salinity. Acclimation to brackish water for 2 weeks improved hypo‐osmoregulatory capacity in both populations, with acclimated fish showing smaller increases in blood plasma ion concentrations, higher Na + ‐K + ATPase activity, and lower mortality than non‐acclimated fish following transfer to 25‰ sea water. Anadromous inconnu maintained pre‐treatment plasma ion levels during acclimation, whereas these levels increased during acclimation in freshwater inconnu. Juvenile anadromous inconnu are therefore able to adapt physiologically to sea water of at least 25‰, if brackish‐water acclimation is available, but freshwater inconnu have diminished saltwater tolerance, relative to the anadromous form.
Osmoregulation
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Semelparity and iteroparity
Hatchery
Broodstock
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Of anadromous Dolly Varden (Salvelinus malma) migrating from the sea into Hood Bay Creek, Admiralty Island, and two other nonlake streams nearby, 61–87% were immature. Most of the immature fish left the streams within a few days of entering. Though nearly all smolts leaving the creek for 3 yr were marked, only 16–21% of the immature fish entering the stream bore these marks. Many of the fish marked in the creek as smolt were recovered entering the two other study streams as immature fish but not as spawners.Mature immigrants remained in the streams for several weeks until they had completed spawning in October and November. Most Dolly Varden that spawned in the creek had been marked there previously as smolt or as spawners, and none were observed to spawn in a stream other than the stream of origin. Smolts transplanted during their oceanward migration returned to spawn in the receiving stream, and adults displaced to saltwater sites on returning to the study streams returned to their home streams. Most fish from the creek spawned only once or twice. Males suffered a much higher spawning mortality than did females.This study and others on fish from lake-stream systems suggest that (1) anadromous Dolly Varden from nonlake streams in southeastern Alaska migrate both between nonlake streams and between nonlake streams and lake-stream systems; (2) during their first summer in the sea, fish from nonlake streams enter several streams while searching for one with a lake; (3) mature fish from nonlake streams leave their wintering area, usually a lake, and return to their home streams to spawn; and (4) mature fish from lake-stream systems go to the ocean to feed for several weeks to a few months and return to their home system to spawn and overwinter.
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The techniques of Instream Flow Incremental Methodology were used to determine the habitat available over a range of simulated streamflows for anadromous fish in certain reaches of streams in the Stillaguamish River basin, Washington. The stream discharge-habitat relations were used to identify that discharge termed the optimum discharge, which provides maximum habitat, for a particular species and life stage of fish. Optimum discharges varied throughout the Stillaguamish River basin because each discharge-habitat relation was unique. The mainstem of the Stillaguamish River is used primarily as a migration route by anadromous fish, but it is also used by chinook and coho salmon and steelhead trout for rearing and by steelhead adults and pink salmon for spawning. Optimum discharges, in cu ft/sec, ranged as follows in the mainstem Stillaguamish River: chinook fry, 600; steelhead--juveniles, 1,000, adults, 2,000, coho juveniles, 400; and pink spawning, 800. The North Fork Stillaguamish River is used for spawning and rearing by all the study fish species. Optimum discharges there were: chinook--spawning, 500 to 1,300, fry, 150 to 400; coho--spawning , 500 to 700, juveniles and fry, 50 to 200; steelhead--adults, 500 to 1,170, spawning, 800 to 900, fry, 50 to 140, juveniles, 300 to 500, chum spawning, 200 to 600; pink spawning, 300 to 600. All the study species spawn and rear in the South Fork Stillaguamish River, but coho spawn and rear fry only at the most upstream study site and chum spawn only at the most downstream site. Optimum discharge ranges on the South Fork were: chinook--spawning, 300 to 900, fry, 70 to 300; coho juveniles, 50 to 100; steelhead--adults, 300 to 900; spawning, 250 to 1,200, fry, 45 to 1,600, juveniles 200 to 500, pink spawning, 100 to 1,200; coho--spawning, 140, fry, 50; chum spawning, 100. Four tributary streams are used by all species except Pilchuck and Canyon Creeks, which are not used by chum salmon. Optimum discharges for all tributary streams ranged as follows: chinook--spawning, 170 to 750, fry 50 to 170; coho--spawning, 90 to 350, fry 20 to 80, juveniles, 35 to 130; steelhead--adults, 170 to 500, spawning, 130 to 400, fry, 20 to 70, juveniles, 70 to 350; pink spawning, 70 to 300; chum spawning in Squire Creek and Jim Creek, 70 to 450. Water temperatures measured in late summer at all sites ranged between 14.5 to 17.5 C. (Lantz-PTT)
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Chinook wind
Fish measurement
Loricariidae
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Alosa
Overwintering
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Not Available – First paragraph follows: California has the southernmost West Coast populations of sea-run or "anadromous" fish, which spawn in fresh water but spend part of their lives in the ocean. The 13 anadromous fish species native to California include chinook salmon, steelhead trout, river lamprey, white sturgeon and longfin smelt.
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Chinook wind
Smelt
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