Working on the unceded territory of the K’ómoks First Nation .

Working with the K’ómoks Nation towards Q’waq’wala7owkw on their unceded territory.

The Importance of Estuarine Environments for Pacific Salmon

Pink Salmon (Oncorhynchus gorbuscha) – E. Jones

There are 8 unique and 11 shared species in marsh, 15 unique and 22  shared species in eelgrass, and 1 unique and 21 shared species in sand flat habitat.

Fish monitoring at Hollyhock flats will be starting this summer! We've summarized a scientific article explaining what kinds of habitat are important to salmonids.

 The article Habitat use by juvenile salmon, other migratory fish, and resident fish species underscores the importance of estuarine habitat mosaics contends that limited and degraded estuarine environments pose a large obstacle to salmon survival. As they leave rivers, salmon enter and stay in estuaries before migrating to the ocean. All Pacific salmon species use estuarine habitats during their downstream migrations, with some residing there for days to months.  Therefore, the abundance and quality of the habitat in estuaries greatly impacts salmon survival rates.

Determining the significance of estuarine habitats is complex. An estuary is subject to daily tidal variations and fluctuations from seasonal changes in temperature and hydrology. To compound the issue, each species using an estuary has a unique life-cycle pattern.

The Fraser River, where the study was conducted, is a primary source of freshwater and significantly impacts the marine ecosystem surrounding it. It supplies essential terrestrial nutrients that support the fish communities and influences the migration routes of emigrating salmon and it governs the nutrient cycling processes of the surrounding Salish Sea. The estuary’s lower reaches serve as crucial habitat for over 50 fish species, including those found in freshwater, estuarine, and marine environments. 

Over 70% of the Fraser River estuarine habitat has been lost or disconnected due to habitat degradation, shoreline modification, alteration of hydrology, nutrient and waste runoff, and noise pollution from industrial, agricultural, and urban development.

Within what remains of the Fraser River estuarine environment, there are three habitats used by salmonoids and other migrating fish: seagrass, marsh, and sand flats, which together form a ‘seascape’. The article found that in terms of estuarine fish species richness and abundance, eelgrass made the largest contribution and exhibited the greatest seasonal variation. While marsh habitat supported the fewest species, it supported more distinct species as compared to sand flat and was particularly preferred by juveniles of the five commercially significant Pacific salmon species. In the Fraser River estuary, marsh was found to be the most used habitat by migrating salmon.

Concerning Pacific salmon species in the Fraser River Estuary, the authors of the study concluded that concentrating exclusively on eelgrass habitat remediation could exacerbate the reduction in salmon populations by depriving them of the remaining marsh. This highlights the idea that interconnected seascapes comprising various habitat types support higher biodiversity and productivity.

Chalifour L, Scott DC, MacDuffee M, Iacarella JC, Martin TG, Baum JK (2019) Habitat use by juvenile salmon, other migratory fish, and resident fish species underscores the importance of estuarine habitat mosaics. Mar Ecol Prog Ser 625:145-162.

Eelgrass

EElgrass (Zostera marina) is a seagrass that grow to create vast underwater meadows, commonly referred to as eelgrass beds.

Sand Flat

Regularly disturbed by wave action and tidal fluctuation and lacking vegitation. 

Marsh

A type of wetland that is dominated by herbaceous species. They form a transition between the aquatic and terrestrial ecosystems.

Related Posts

Forage Fish Symposium and CFFN AGM

The Coastal Forage Fish Network is hosting their Annual Spring symposium via zoom on April 23, 2025, from 6:00-8:00 pm. It will be followed by an AGM. This gathering brings together researchers, experts and community science volunteers to share forage fish research highlights and from across Vancouver Island and beyond.

Kus-kus-sum Feature – Spring 2025

As spring kicks off, the first buds are beginning to appear on the newly installed plants down at Kus-kus-sum! Thanks to the efforts of our volunteers this past fall and winter we’ve been able to expand the now thriving tidal marsh and riparian ecosystems to 80% complete.

Spring Invasives Removal at Kus-kus-sum

We are looking for volunteers to assist us with our first weeding event of the spring at Kus-kus-sum to keep the invasives at bay and help our native plants flourish!

How To Report Herring Spawn Sightings on iNaturalist

Want to contribute to community science while walking the beach? Simply snap a photo of Pacific herring eggs or milt (milky-white water) when you come across them and upload your observations to iNaturalist! Keep reading for instructions.