The feeding dynamics of out-migrated age-0 chinook salmon (Oncorhynchus tshawytscha) in Lake Ontario
Notice bibliographique
Résumé
The purpose of this study was to examine gastric evacuation, feeding chronology, daily ration, growth, diet, and prey selectivity of recently out-migrated young-of-the-year (YOY) chinook salmon (Oncorhynchus tshawytscha) in Lake Ontario. To determine gastric evacuation rates, chinook salmon ranging from 40-80 mm in total length, were fed to satiation and maintained at 10, 13, 16, or 19oC in the laboratory for 24 hours. Five fish were sampled randomly every four hours from each temperature treatment and the complete digestive tract (CDT) contents were removed. The CDT contents and the remainder of each fish were subsequently dried and weighed. Results show that evacuation rate (R) was dependent on temperature, with estimates of R ranging from 0.214?h-1 to 0.352?h-1, at 10oC and 19oC, respectively. Field sampling for daily ration estimates was conducted on five dates from May 21 ? June 25, 2001. Sub-yearling chinook salmon were captured using a seine near the mouth of the Salmon River, beginning 30-60 minutes after sunrise and continuing at approximately 4-hour intervals for 24 hours. Estimates of mean daily ration ( ) were derived using the Eggers (1977) model. Results showed that gut fullness varied significantly (p < 0.05) with both date and time of day, but there was no indication of synchronous diel variability in gut fullness between dates. Because did not vary as a function of date (p > 0.05), an overall (28.3 g dry wt?100 g dry wt-1?d-1) was calculated using the grand mean for all five sampling dates. Daily ring counts of sagittal otoliths revealed that in 2001, YOY chinook hatched between February 21 and April 2, and exhibited a mean growth rate of 0.65 mm?day-1. The early spring hatch dates indicated that the captured chinook salmon were naturally produced, as 2001 hatchery chinook hatched in November. For diet analyses, out-migrated YOY chinook salmon, along with potential prey items, were sampled biweekly, at dusk, at two near-shore sites (i.e., Sandy Creek and the Salmon River) in Lake Ontario from April ? July of 2000. In 2001, weekly diet and prey sampling was conducted from April ? July at the Salmon River site only. On five dates from mid-May to late-June 2001, prey and fish samples were collected throughout the day to assess diel shifts in prey availability and selection. Mid-water and surface prey sampling was conducted using a 1000 ?m neuston net pulled across the surface and parallel to the shoreline in water about one meter deep. Out-migrated, age-0 chinook salmon were captured using a seine concurrent with prey samples in both 2000 and 2001. Results showed that YOY chinook salmon in Lake Ontario were primarily diurnal feeders as indicated by both a decrease in gut content wet weight and the lack of identifiable prey in stomach samples examined after midnight. Sub-yearling chinook sampled at dusk at both sites in 2000 and 2001 fed heavily on aquatic taxa, with mature chironomids constituting the bulk of the diet. Similarly, chinook salmon sampled during the day at the Salmon River site in 2001 consumed at least 71% aquatic taxa. Moreover, there was little evidence of a diel diet shift. Although amphipods, homopterans, and developing chironomidae often dominated the prey samples, daytime diet data collected at the Salmon River site in 2001 revealed that mature chironomidae remained the most frequently consumed prey. Strauss?s (1979) index of prey selection (L) revealed that in general, YOY chinook actively selected (L = 0.3-0.5) for chironomidae, while negatively selecting for non-chironomids. This study shows that naturally produced chinook salmon are thriving in the near-shore areas of Lake Ontario and consequently have an excellent chance to recruit to the lake?s Pacific salmon fishery.
Récupéré en direct depuis OpenAlex et désinversé. Les résumés ne sont pas conservés dans cette base de données : les index inversés représentent 8,6 Go des 9,3 Go de texte de la base, et le serveur dispose de 13 Go libres.
Comment cette classification a été obtenuedéplier
Prédiction machine sur la base complète
Imitation des enseignantsNi prévalence calibrée, ni vérité terrain. Validation humaine à venir. Le volet Gemma est une étiquette directe du modèle pour chaque travail de la base, lue sur la notice réduite au titre. Le volet Codex est un classifieur appris des 10 348 étiquettes directes de Codex et calibré sur les taux pondérés de l'échantillon; les champs sans appui suffisant ne portent aucun appel Codex. Le mode candidate est l'union des deux volets; le consensus est leur intersection. Ces sorties portent le statut machine_predicted_unvalidated et ne sont pas des étiquettes humaines.
Scores du classifieur distillé par catégorie (deux têtes)
| Catégorie | Codex | Gemma |
|---|---|---|
| Métarecherche | 0,000 | 0,000 |
| Méta-épidémiologie (sens strict) | 0,000 | 0,000 |
| Méta-épidémiologie (sens large) | 0,000 | 0,000 |
| Bibliométrie | 0,000 | 0,000 |
| Études des sciences et des technologies | 0,001 | 0,000 |
| Communication savante | 0,000 | 0,000 |
| Science ouverte | 0,000 | 0,000 |
| Intégrité de la recherche | 0,000 | 0,000 |
| Charge utile insuffisante (le modèle a refusé de juger) | 0,001 | 0,000 |
Scores machine (provisoires)
Les deux têtes enseignantes du modèle étudiant, lues sur ce travail. Un score ordonne la base pour la relecture; il n'affirme jamais une catégorie, et le statut de validation accompagne chaque rangée tel quel.
Scores de référence d'un modèle non mature (critères de maturité non atteints, 7 itérations). Un score ordonne; il n'affirme jamais une catégorie.
score_only:v0-immature-baseline · tel quel depuis la passe de notation : score_only signifie que le nombre peut ordonner les travaux, et qu'aucune étiquette de catégorie n'en découleClassification
machine, non validéePrédiction automatique; un appel candidat d’une seule source (Gemma direct ou Codex distillé), pas un consensus.
Le détail, modèle par modèle et score par score, se trouve en fin de page sous « Comment cette classification a été obtenue ».