Decline in Feeding Activity of Female Cultured Delta Smelt Prior to Spawning

Hung, Tien‐Chieh; Eder, Kai J.; Javidmehr, Alireza; Loge, Frank J.

doi:10.1080/15222055.2014.886650

Cited by 3 publications

(3 citation statements)

References 15 publications

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“…Recent work demonstrated the importance of minnow CUE in spring on lake trout feeding patterns, and that autumn minnow CUE had little impact on lake trout feeding behaviour (Guzzo, Blanchfield, & Rennie, ). Furthermore, fish often reduce their feeding rates in advance of spawning (Fordham & Trippel, ; Hung, Eder, Javidmehr, & Loge, ; Krumsick & Rose, ), which may limit resource use of abundant minnows in autumn by lake trout. Foraging on small fish prey by lake trout (e.g.…”

Section: Discussionmentioning

confidence: 99%

Impacts of freshwater aquaculture on fish communities: A whole‐ecosystem experimental approach

et al. 2019

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Aquaculture is a growing global industry; freshwater aquaculture has significant potential for expansion in Canada, but growth of the freshwater sector has been slow due to concerns over potential environmental impacts and a lack of information on potential impacts to native fish communities. To provide guidelines and target variables for evaluating aquaculture impacts on freshwater fish communities, we operated an experimental aquaculture farm as a whole‐lake experiment where 10,000 rainbow trout (Oncorhynchus mykiss) were raised annually from 2003 to 2007. Impacts were assessed using up to 8 years of pre‐impact and 8–10 years of post‐impact data. Prey fish abundance increased dramatically during aquaculture but declined sharply following the experiment. High abundance of littoral minnows in autumn was not observed during spring and, combined with size distribution data, suggests high overwinter mortality of adult minnows. White sucker (Catostomus commersonii) abundance and body condition declined during and after aquaculture, with evidence of overwinter juvenile recruitment failure in the last 2 years of operation, although size‐at‐age increased. The adult abundance of lake trout (Salvelinus namaycush) doubled during aquaculture, due to a combination of (a) increased growth rates of young trout and (b) earlier age and larger sizes at maturation. Within 2 years following aquaculture, lake trout abundance declined by nearly 50% to background levels, suggesting a large increase in lake trout mortality once operations ceased. These changes were not observed in nearby reference lakes. While aquaculture appeared to benefit some species (slimy sculpin [Cottus cognatus], minnows, lake trout), prolonged declines in white sucker abundance and condition and continued depression of Mysis densities and optimal oxythermal habitat availability nearly a decade following operations suggest potentially long‐term impacts at this magnitude. Importantly, this experiment highlights important indicator species and life history traits for monitoring of freshwater aquaculture impacts on native fish communities.

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Section: Discussionmentioning

confidence: 99%

Impacts of freshwater aquaculture on fish communities: A whole‐ecosystem experimental approach

et al. 2019

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“…Another possibility is that the DWSC site deployment overlapped with the natural period of gamete production based on water temperatures [51], which may focus energy on gamete production and away from somatic growth. Captive-reared Delta Smelt females tend to reduce their feed intake considerably as they near spawning [52]. Lastly, fish transferred from the FCCL to the DWSC site were acclimated at the FCCL for 35 days longer than the fish used at the RV site.…”

Section: Plos Onementioning

confidence: 99%

Captive-reared Delta Smelt (Hypomesus transpacificus) exhibit high survival in natural conditions using in situ enclosures

Baerwald¹,

Kwan²,

Pien³

et al. 2023

PLoS ONE

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Conservation of endangered fishes commonly includes captive breeding, applied research, and management. Since 1996, a captive breeding program has existed for the federally threatened and California endangered Delta Smelt Hypomesus transpacificus, an osmerid fish endemic to the upper San Francisco Estuary. Although this program serves as a captive refuge population, with experimental releases being initiated to supplement the wild population, it was uncertain how individuals would survive, feed, and maintain condition outside hatchery conditions. We evaluated this and the effects of three enclosure designs (41% open, 63% open, and 63% open with partial outer mesh wrap) on growth, survival, and feeding efficacy of cultured Delta Smelt at two locations (Sacramento River near Rio Vista, CA and in Sacramento River Deepwater Ship Channel) in the wild. Enclosures exposed fish to semi-natural conditions (ambient environmental fluctuations and wild food resources) but prevented escape and predation. After four weeks, survival was high for all enclosure types (94–100%) at both locations. The change in condition and weight was variable between sites, increasing at the first location but decreasing at the second location. Gut content analysis showed that fish consumed wild zooplankton that came into the enclosures. Cumulatively, results show that captive-reared Delta Smelt can survive and forage successfully when housed in enclosures under semi-natural conditions in the wild. When comparing enclosure types, we observed no significant difference in fish weight changes (p = 0.58–0.81 across sites). The success of housing captive-reared Delta Smelt in enclosures in the wild provides preliminary evidence that these fish may be suitable to supplement the wild population in the San Francisco Estuary. Furthermore, these enclosures are a new tool to test the efficacy of habitat management actions or to acclimate fish to wild conditions as a soft release strategy for recently initiated supplementation efforts.

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“…Therefore food availability for adults is critically important for income breeders for their reproduction. Although Delta Smelt is a multiple spawner as indicated by the presence of immature oocytes in the gonad of fully mature females by histology [38], Delta Smelt could be a capital breeder since (1) reduction in feeding activity was observed prior to and during the spawning season in the wild and at a fish culture facility [28,79] and (2) atrophic oocytes are rarely found in wild and cultured fish by histology (Personal observation). Further investigation is needed since the reduction in feeding activity during the spawning season in the wild may be because of other causes such as food availability or abiotic factors such as lower water temperatures.…”

Section: Plos Onementioning

confidence: 99%

Reproductive strategy of Delta Smelt Hypomesus transpacificus and impacts of drought on reproductive performance

et al. 2022

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Understanding reproductive biology and performance of fish is essential to formulate effective conservation and management programs. Here, we studied reproductive strategies of female Delta Smelt Hypomesus transpacificus, an endangered fish species in the State of California, the United States, focusing on (1) better understanding their distribution pattern during the winter and spring spawning season at very fine scale to predict their possible spawning grounds and (2) assessing impacts of a recent, severe drought on their reproductive performance. We formulated our hypotheses as follows; (1) female Delta Smelt migrate to particular locations for spawning so that mature females can be frequently found in those locations throughout the spawning season and (2) reproductive performance of individual female fish declined during the drought. To test the first hypotheses, we analyzed relationships between water quality parameters and maturity/distribution pattern of Delta Smelt. Salinity better explained the distribution pattern of Delta Smelt at subadult and adult stages compared with water temperature or turbidity. Although there are some freshwater locations where mature Delta Smelt can frequently be found during the spawning season, Delta Smelt at the final maturation stage (Stage 5: hydration) and post spawners appeared to be widespread in the area where salinity was below 1.0 during the spawning season. Therefore, Delta Smelt could theoretically spawn in any freshwater locations, with more specific spawning requirements in the wild (e.g., substrate type and depth) still unknown. Delta Smelt, which experienced dry and critically dry conditions (the 2013 and 2014 year-classes), showed smaller oocytes, and lower clutch size and gonadosomatic index compared with the fish caught in a wet year (2011 year-class) at the late vitellogenic stage (Stage 4 Late), suggesting reproductive performance was negatively affected by environmental conditions during the drought.

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Decline in Feeding Activity of Female Cultured Delta Smelt Prior to Spawning

Cited by 3 publications

References 15 publications

Impacts of freshwater aquaculture on fish communities: A whole‐ecosystem experimental approach

Impacts of freshwater aquaculture on fish communities: A whole‐ecosystem experimental approach

Captive-reared Delta Smelt (Hypomesus transpacificus) exhibit high survival in natural conditions using in situ enclosures

Reproductive strategy of Delta Smelt Hypomesus transpacificus and impacts of drought on reproductive performance

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