Differentiated predation risk on hatchery-reared juvenile masu salmon by white-spotted charr with different body sizes

Miyamoto, Kouta; Araki, Hideki

doi:10.1007/s12562-016-1059-8

Cited by 7 publications

(7 citation statements)

References 47 publications

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“…Values shown in italics show fork lengths of white-spotted charr that did (red) and did not (black) prey on masu salmon fry. Bold values above the dashed lines indicate the theoretical minimum white-spotted charr fork length needed to prey upon masu salmon fry of the fork length [23] shown below the dashed line.…”

Section: Resultsmentioning

confidence: 99%

“…However, the consumption of stocked masu salmon fry contributed to an increase in the stomach contents of white-spotted charr, especially the larger individuals. This suggests that IG predation occurred depending on the relative body size difference between IG predators and IG prey [ 23 ], and importantly the pulsed supply of IG prey can contribute to an increase in the food intake of IG predators, despite the simultaneous interspecific competition for food resources. However, the occurrence of IG predation in our study was time-limited.…”

Section: Discussionmentioning

confidence: 99%

“…Of these, white-spotted charr were common to all study sites and were therefore deemed the target IG predators. A previous study demonstrated that white-spotted charr frequently preyed upon masu salmon if the fork length of the masu salmon was less than 40% that of the white-spotted charr [ 23 ]. Water temperatures in the study sites were typical for streams inhabited by salmonids (electronic supplementary material, table S1).…”

Section: Methodsmentioning

confidence: 99%

“…Body size (fork length: mm) histograms of stocked masu salmon fry and fork length (mm) of each experimental whitespotted charr in each stocked stream (a: Gunkai; b: Uchiyama; c: Matsumura; d: headstream of the Mena River) in each study period.Values shown in italics show fork lengths of white-spotted charr that did (red) and did not (black) prey on masu salmon fry. Bold values above the dashed lines indicate the theoretical minimum white-spotted charr fork length needed to prey upon masu salmon fry of the fork length[23] shown below the dashed line.…”

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confidence: 99%

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Pulsed supplies of small fish facilitate time-limited intraguild predation in salmon-stocked streams

Hasegawa

Fukui

2022

R. Soc. open sci.

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Pulsed supplies of prey generally increase predator food intake. However, it is unclear whether this holds true when predators and pulsed prey are in the same guild (i.e. intraguild (IG) predators and prey). IG prey may increase IG-predator food intake through predation, but they may decrease food intake through competition. To test these hypotheses, we compared the food intake of white-spotted charr ( Salvelinus leucomaenis ) (IG predator) in streams that were stocked or unstocked with masu salmon ( Oncorhynchus masou ) fry (IG prey) in streams in Hokkaido, Japan. One day after stocking, mean stomach content weight of charr was six times higher than in unstocked streams due to fry consumption. In particular, large charr showed intense piscivory. However, predation on fry was rare after about three weeks. Some factors that could explain this time-limited IG predation include the growth and decreasing abundance of fry over time and the acquisition of predator-avoidance behaviour. In days other than the first-day post-stocking, food intake by charr did not differ between stocked and unstocked streams. No effects of interspecific competition on charr food intake were observed.

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Section: Resultsmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

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Pulsed supplies of small fish facilitate time-limited intraguild predation in salmon-stocked streams

Hasegawa

Fukui

2022

R. Soc. open sci.

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“…2003; Hyvärinen and Vehanen 2004; Osterback et al. 2014; Miyamoto and Araki 2017). Smaller size can also negatively affect overwinter survival (Meyer and Griffith 1997).…”

Section: Discussionmentioning

confidence: 99%

Poststocking Survival and Myxospore Evaluation of Whirling Disease‐Resistant Rainbow Trout Strains

Erickson

Schisler

Fetherman

2023

N American J Fish Manag

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The ensuing spread of whirling disease following its initial introduction in the United States in the late 1950s caused drastic declines in populations of Rainbow Trout Oncorhynchus mykiss. The German Rainbow (GR) strain has strong resistance to Myxobolus cerebralis, the parasite causing whirling disease, but also has an extensive history as a domesticated food-production fish, resulting in traits that are presumed to be maladaptive for survival in the wild. The wild Harrison Lake Rainbow (HAR) strain exhibits reduced infection severity compared with other wild Rainbow Trout strains, but resistance is lower than the GR strain and was considered insufficient to meet management goals. Prior research suggests that crosses of GR with susceptible strains create offspring with Myxobolus cerebralis resistance and survival rates intermediate to the parental strains in lotic environments, but analysis on lentic environments with larger predators has been limited. We evaluated survival rates and infection severities of fingerling Rainbow Trout stocked into a lentic environment from four different strains with theoretically varying resistances to Myxobolus cerebralis: GR, HAR, and an F 1 [GR × HAR(50:50)] and F 2 [GR × HAR(75:25)] crossed strain between the GR and HAR strains. Using Seber dead-recovery models, we found that both the HAR and GR × HAR(50:50) strains had the highest survival rate, followed sequentially by the GR × HAR(75:25) and GR. Whirling disease resistance, as estimated from infection probability and severity, increased with increasing GR strain genetic background. To reduce spore loads and increase resistance in managed Rainbow Trout populations, we suggest stocking strains like the GR × HAR(50:50) that have respectable whirling disease resistance and high survival rates, enabling wild recruitment with increased cost-efficiency of stocking.

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The past, present, and a future for native charr in Japan

Fausch,

Morita,

Tsuboi

et al. 2024

Ichthyol Res

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Charrs (Salvelinus) reach their southernmost distribution in Japan, and are uniquely adapted to the short, steep streams of this island archipelago. Southern Asian Dolly Varden (Salvelinus curilus) occur only in Hokkaido Island, whereas white-spotted charr (Salvelinus leucomaenis) range to southern Honshu. Both species diverged from an ancestral lineage during the late Pliocene/early Pleistocene, when lowered sea levels created semi-enclosed water bodies in the seas of Japan and Okhotsk. Genetic analyses showed S. curilus represents the most ancient divergence from the Dolly Varden (Salvelinus malma) - Arctic charr (Salvelinus alpinus) group, and revealed five lineages of S. leucomaenis which align differently than traditional subspecies. Japanese charr display diverse and flexible life histories including anadromous fish with partial migration, and fluvial, adfluvial, and resident forms. In Hokkaido, Dolly Varden are distributed upstream and white-spotted charr downstream. They coexist in narrow sympatric zones through adaptive shifts by Dolly Varden in behavior and morphology that facilitate benthic foraging. Both species hybridize with native and nonnative salmonids, and are displaced from microhabitats and decline in abundance when rainbow trout (Oncorhynchus mykiss) and brown trout (Salmo trutta) invade. Japan streams contain over 95,000 erosion control dams which create short stream fragments (medians ~200 m). This has increased extirpation of charr populations via lower genetic diversity and stochastic and demographic factors. Tributaries provide complex rearing habitats, afford refuges from floods, and supply recruits that sustain populations in mainstem fragments and create metapopulations in connected riverscapes. Charr play central roles in linked stream-riparian food webs, and cause direct and indirect effects that cascade to streambed algae and riparian predators when linkages are disrupted by anthropogenic effects or altered by native parasites. Many charr populations are threatened by habitat fragmentation and introgression or invasion by nonnative forms, but efforts to conserve charr are growing. These include restoring connectivity among pure populations above barriers that prevent invasions, protecting tributary nurseries, and instituting angling regulations to protect headwater populations. Key steps include inventorying pure populations, identifying conservation units, selecting appropriate management based on connectivity and biotic interactions, and engaging stakeholders and youth to engender an ethic for conserving irreplaceable charr lineages.

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Differentiated predation risk on hatchery-reared juvenile masu salmon by white-spotted charr with different body sizes

Cited by 7 publications

References 47 publications

Pulsed supplies of small fish facilitate time-limited intraguild predation in salmon-stocked streams

Pulsed supplies of small fish facilitate time-limited intraguild predation in salmon-stocked streams

Poststocking Survival and Myxospore Evaluation of Whirling Disease‐Resistant Rainbow Trout Strains

The past, present, and a future for native charr in Japan

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