Diel migration pattern of pink salmon fry in small streams

Katahira

Miura

et al. 2022

Ecology and Evolution

Self Cite

As a spatial subsidy, which is the phenomenon of transferring resources from a donor system to a recipient system, anadromous salmonids contribute to the supply of marine‐derived nutrients to freshwater and terrestrial systems. Live salmon and salmon carcasses and eggs are utilized by various organisms and affect their abundance and distribution. However, the evaluation of the effect of salmon subsidies on the abundance and distribution of terrestrial animals is biased toward predators or scavengers that utilize spawning adults and carcasses, and few studies have focused on the effect of salmon eggs as a subsidy. To avoid underestimating the function of salmon subsidies, the response to the availability of salmon eggs in various systems should be investigated. Here, we investigated the abundance and feeding behavior of the brown dipper Cinclus pallasii, as a consumer of salmon eggs, based on the hypothesis that the availability of salmon eggs affects the diet composition and stream distribution of this small predator. In addition, to test whether changes in the abundance of brown dippers are determined by salmon spawning, their abundance was compared upstream and downstream of the check dams in three streams during the peak spawning period. Brown dippers used salmon eggs during the spawning season (53.7% of diet composition), and their abundance increased as the number of spawning redds increased. In contrast, this pattern was not observed upstream of the check dam. These results suggested that the abundance and stream distribution of brown dippers vary according to the variation in the spatiotemporal availability of salmon eggs.

Section: Discussionmentioning

confidence: 99%

Relationship between salmon egg subsidy and the distribution of an avian predator

Katahira

Miura

et al. 2022

Ecology and Evolution

Self Cite

Section: Discussionmentioning

confidence: 99%

Relationship between salmon egg subsidy and the distribution of an avian predator

Katahira

Miura

et al. 2022

Preprint

Self Cite

As a spatial subsidy, which is the phenomenon of transferring resources from a donor system to a recipient system, anadromous salmonids contribute to the supply of marine-derived nutrients to freshwater and terrestrial systems. Live salmon and salmon carcasses and eggs are utilized by various organisms and affect their abundance and distribution. However, the evaluation of the effect of salmon subsidies on the abundance and distribution of terrestrial animals is biased towards predators or scavengers that utilize spawning adults and carcasses, and few studies have focused on the effect of salmon eggs as a subsidy. To avoid underestimating the function of salmon subsidies, the response to the availability of salmon eggs in various systems should be investigated. Here, we investigated the abundance and feeding behaviour of the brown dipper Cinclus pallasii, as salmon egg a consumer, based on the hypothesis that the availability of salmon eggs affects the diet composition and stream distribution of this small predator. In addition, to test whether changes in the abundance of brown dippers are determined by salmon spawning or by other factors, their abundance was compared upstream and downstream of the dam. Brown dippers used salmon eggs during the spawning season (63% of diet composition), and their abundance increased as the number of spawning redds increased. In contrast, this pattern was not observed upstream of the dam. These results suggested that the abundance and stream distribution of brown dippers vary according to the variation in the spatiotemporal availability of salmon eggs.

“…We used stakes to fix the nets to the streambed so that the net openings spanned from the stream surface to the streambed. All surveys started between 18:00 and 18:30 and finished between 22:15 and 22:45 because downstream migration of pink salmon fry is almost always observed at night (Kirillov et al, 2018;Neave, 1955), and its peak was found at approximately 20:00 in this study area (Yamada, Urabe, et al, 2022). However, if pink salmon fry were not collected throughout the first to fourth trials, the survey was finished between 21:15 and 21:45.…”

Section: -3 Estimation Of the Total Number Of Fry Migrantsmentioning

confidence: 99%

“…We placed one or two drift nets (Matsui Corp., Tokyo, Japan; 50 cm squared opening, 100 cm long, 3 mm mesh), which are often used to capture salmon fry (Hintz & Lonzarich, 2012;T. A. Johnston, 1997;Yamada, Urabe, et al, 2022), at a sampling point for 15 minutes at hourly intervals (Yamada, Urabe, et al, 2022). Since long-term sampling with drift nets would result in higher fry mortality, we set the sampling duration to be as short as possible.…”

Section: -3 Estimation Of the Total Number Of Fry Migrantsmentioning

confidence: 99%

“…where C D , F D , andS D are captured fry, water filtered by drift nets, and stream discharge on day D , respectively. In the equation, "4" is the value used to convert the number of migrants per 15 minutes to that per hour, and "0.899" is the proportion of fry that migrated during the survey time relative to the whole sampling day, as indicated by Yamada, Urabe et al (2022). We also determined the total number of pink salmon fry during the sampling period per stream using the AUC estimation method (Bue et al, 1998;English et al, 1992).…”

Section: -3 Estimation Of the Total Number Of Fry Migrantsmentioning

confidence: 99%

See 1 more Smart Citation

Watershed hydrogeomorphology drives freshwater productivity of anadromous salmonids: Implications for habitat conservation and restoration

Urabe

Nakamura

2023

Preprint

Considering the spatial omnipresence of the threat to biodiversity and limited resources and time for conservation and restoration, it is crucial to prioritize conservation and restoration activities to maximize benefits. By transporting marine-derived nutrients to freshwater and surrounding ecosystems, anadromous salmonids contribute greatly to biodiversity maintenance; however, their abundance has been decreased by human activities in many regions. Salmon populations are mainly governed by their productivity in the freshwater life stage; therefore, freshwater productivity, namely, the number of juveniles migrating to the ocean per reproducing parent, should be investigated to maintain healthy populations. Given that productivity decreases dramatically in response to flooding, the flood disturbance intensity controlled by hydrogeomorphology at a watershed scale may strongly influence the freshwater productivity of salmonids. In this study, we evaluated the effect of watershed hydrogeomorphology on the productivity of pink salmon (Oncorhynchus gorbuscha). We surveyed the escapement and number of fry migrants of pink salmon and measured environmental factors, including the average watershed slope and stream power index, as parameters of hydrogeomorphology. The freshwater productivity of pink salmon differed among the streams investigated and was negatively affected by average watershed slope, stream power, and average watershed maximum daily precipitation. These results indicated that flood disturbance reduces the freshwater productivity of pink salmon and that salmon productivity in an individual stream can be predicted by watershed hydrogeomorphology. Our approach can be applied to other anadromous salmonids that have spawning behaviour similar to that of pink salmon, which bury eggs in gravel. Predicting highly productive habitats based on the present study can contribute to planning and prioritizing habitat conservation and restoration for anadromous salmonids.