Live blog of a talk entitled “Managing Puget Sound’s Groundfish Resources from the Bottom Up“ by Wayne Palsson at NWFSC
11:00 Background/motivation
28 species of rockfish, but poor habitat maps (compared with spotted owls, say)
Decline of groundfish like Pacific Cod in south Puget Sound has been prominent in last 10-15 years. Walleye pollock is endangered; 18 species were covered in ESA petitions in 1999. Many PS species are vulnerable. Copper and quillback petition was judged not warranted in 2006. 2007 petitions are pending for ~5 species.
Lingcod is an exception. North and south populations have been increasing since about 1995. Fisheries were restricted ~1990 after overfishing in late 70’s and early 80’s (big drop in catch/trip in 84-85).
11;17 History of habitat studies:
- Miller mid-1970s — nearshore habitat surveys
- Moulton 1977
- Cross 1991, Rocky intertidal
- Becker 1984, English sole
- Richards 86-87, depth substrate, relief (sub-based?)
- Matthews, 1990abc, rockfish, telemetry
- Murie, 1994, depth, complexity, wall
Rockfish, lingcod, greenling are associated with boulders and walls
Null hypotheses:
- Fish are randomly distributed
- Distributions are independent of: depth, substrate, slope, complexity, water quality, time, light, food, life stage
11:23 Showed map of continuous bathymetry map in a GIS for all PS, N to Pt. Roberts, and offshore to about outer boundary of Sanctuary
11:24 Bottom trawl surveys (since 1987, ~only in springtime) yield maps with consistent coverage that gets sparse only in SJdF and Georgia Strai [~200 trawls in San Juan Islands since 2001; about 130 are within uniform substrate areas)
- Starry flounder associated with shallower water
- Some English sole in S Haro Strait
- Three geographic groups of similar species: Western Strait of Juan de Fuca, N Puget Sound, and S Puget Sound
- Depth patterns: Dover, Hake, Skate are deep species > 120 fathoms; Dogfish and English sole are at all depths
- Substrate patterns (based on Gary Greene’s multibeam data):
- flathead sole characteristic of deep mud stations
- ROV surveys in San Juan Channel (58 in 2004; 70+ in 2005) reveal:
- rockfish like rocks (especially copper and quillback), so do lingcod and greenling
11:43 Drop camera results (consistent with ROV results)
Philip Block got substrate maps out of NOAA, but still have need for better seafloor maps in the Salish Sea…
11:47 Conclusions: managing from the bottom up
200-300 ROV transects in the San Juans happening now!
11:49 Questions
- seasonality? is a factor, but we’ve not looked for it yet
- what are threats to sub-tidal habitats? Not clear what really matters, but likely factors are trawling and climate change
- Recreational fishing is a threat to rockfish populations (see recent stock assessment)
- What’s controlling population structure? Fishing, climate change, marine mammal predation… We can probably recover from all these… Ling cod are now dominant biomass at Edmonds.
12:01 end