Effects of Sea Level Rise on the Spawning Habitat of Two Beach Spawning Fishes

Surf Smelt (Hypomesus pretiosus) and Pacific Sand Lance (Ammodytes hexapterus) are vital to the Salish Sea ecosystem â€"providing forage for many marine mammals, sea birds, and other fish species (Wilson 1995).

Pacific Sand Lance and Surf Smelt spawn on beaches (Penttila1995 ), likely as a means of reducing predation of eggs (Martin and Swiderski 2001).

Global warming is expected to elevate sea level 0.08 m (range 0.3 -0.13) by 2025 and 0.39 m (range 0.13 -0.69 m) by 2100 (Bates et al. 2008).

Sea level rise might result in a loss of forage fish spawning habitat on beaches constrained by shoreline armoring. As sea level rises, the elevation difference between the �"new” Mean Lower Low Water (MLLW) and the toe of the bulkhead decreases, effectively eliminating a portion of the upper beach that serves as spawning habitat for forage fish.

Our goal was to estimate the magnitude of egg loss due to contraction of spawning habitat resulting from sea level rise on armored beaches.

Our analysis assumes:

1. egg distribution as a function of beach elevation will remain constant, notwithstanding changes due to armoring,
2. our data and methods adequately describe spawning distributions, and
3. elevation of armoring is the Ordinary High Water Mark estimated at MHHW + 1.5 feet.