Juvenile Pacific salmon (Oncorhynchus spp.), ecologically-related species, and associated biophysical data were collected from the marine waters of the northern region of southeastern Alaska (SEAK) in 2015. This annual survey, conducted by the Southeast Coastal Monitoring (SECM) project, marks 19 consecutive years of systematically monitoring how juvenile salmon utilize marine ecosystems during a period of climate change. The survey was implemented to identify the relationships between year-class strength of juvenile salmon and biophysical parameters that influence their habitat use, marine growth, prey fields, predation, and stock interactions. Up to 13 stations were sampled monthly in epipelagic waters from May to August (total of 23 sampling days). Fish, zooplankton, surface water samples, and physical profile data were collected during daylight at each station using a surface rope trawl, bongo nets, a water sampler, and a conductivity-temperature-depth profiler. Surface (3-m) temperatures and salinities ranged from approximately 8 to 15 ºC and 15 to 32 PSU across inshore, strait, and coastal habitats for the four months. A total of 17,228 fish and squid, representing 25 taxa, were captured in 92 rope trawl hauls fished from June to August. Juvenile salmon comprised approximately 89% of the catch. Over all months and habitats, juvenile pink (O. gorbuscha), chum (O. keta), sockeye (O. nerka), and coho (O. kisutch) salmon occurred in 51-92% of the hauls, while juvenile Chinook salmon (O. tshawytscha) occurred in about 22% of the hauls. Abundance of juvenile salmon was low in 2015; peak CPUE occurred in June strait and coastal habitats. Coded-wire tags were recovered from 51 juvenile coho salmon and 5 juvenile and immature Chinook salmon, that primarily originated from hatchery and wild stocks in SEAK sampled in the strait habitat; an additional 18 adipose-clipped juvenile salmon without tags were present. The only non-Alaskan stocks were recovered off Icy Point, a juvenile Chinook salmon from the Willamette River, OR and a juvenile coho salmon from the Satsop River, Washington. Of the juvenile salmon examined for otolith marks, Alaska enhanced stocks comprised 56% of the juvenile chum (373 of 663) and 38% of the juvenile sockeye salmon (202 of 532). Of the 380 potential predators of juvenile salmon, predation on juvenile salmon was not observed in the six fish species examined. The long term seasonal time series of SECM juvenile salmon stock assessment and biophysical data is used in conjunction with basin-scale ecosystem metrics to annually forecast pink salmon harvest in SEAK. Long term seasonal monitoring of key stocks of juvenile salmon and associated ecologically-related species, including fish predators and prey, permits researchers to understand how growth, abundance, and interactions affect year-class strength of salmon in marine ecosystems during a period of rapid climate change.