Scott W. Johnson

Distribution, Habitat, and Behavior of Rockfishes, Sebastes spp., in Nearshore Waters of Southeastern Alaska: Observations From a Remotely Operated Vehicle

We examined distribution, habitat, and behavior of rockfishes, Sebastes spp., with a remotely operated vehicle (ROV) in coastal waters <90 m deep of southeastern Alaska from 1998 to 2000. We identified black, S. melanops, canary, S. pinniger, China, S. nebulosus, copper, S. caurinus, dusky, S. ciliatus, harlequin, S. variegatus, Puget Sound, S. emphaeus, quillback, S. maliger, redstripe, S. proriger, rosethorn, S. helvomaculatus, silvergray, S. brevispinis, tiger, S. nigrocinctus, yelloweye, S. ruberrimus, and yellowtail, S. flavidus, rockfish. Quillback and dusky rockfish were the most widely distributed species, China and harlequin rockfish were the least widely distributed species. Species richness was greater at sites on or near the outer coast than at sites in more inside, sheltered waters. Most (>75%) observations of rockfish were over complex bottoms of boulder and rock or in vertical bedrock wall habitats. Few rockfish were observed over soft bottoms with no relief. Median depth of observation was ≤30 m for black, copper, dusky, and yellowtail rockfish and >30 m for all other species. Median temperature of observation ranged from 6.1°C for harlequin rockfish to 9.4°C for black rockfish. Size of fish was positively correlated (p ≤ 0.036) with depth for dusky, quillback, and yelloweye rockfish. Species often observed alone were China (67%), copper (46%), quillback (46%), and rosethorn (43%) rockfish. Most (≥70%) observations of harlequin, Puget Sound, silvergray, tiger, and yelloweye rockfish were in mixed species assemblages. When first observed, the behavior of most rockfish species was swimming or hovering. Notable exceptions were China, harlequin, rosethorn, and tiger rockfish; 33–57% were resting on bottom or in a hole or crevice.

Effects of Logging on the Abundance and Seasonal Distribution of Juvenile Steelhead in Some Southeastern Alaska Streams

Abstract Eighteen streams in six locations in southeastern Alaska were examined for the effects of logging on juvenile steelhead (Salmo gairdneri) populations. Three types of streams were examined at each location: a stream in undisturbed old-growth forest; a stream in a clear-cut area with strips of forest (buffer strips) along the stream bank; and a stream in a clear-cut area logged on at least one bank. Within each stream type, three reaches were sampled. Few juvenile steelhead were found in reaches where juvenile cutthroat trout (Salmo clarki) were present, and no juvenile steelhead were found in streams with a low-flow discharge (<0.06 m 3/s). Only two study sites, Prince of Wales Island and Mitkof Island, had juvenile steelhead in all three stream types. Fry (age 0) and parr (age I and older) were sampled in summer and winter at the Prince of Wales Island site; parr were sampled in summer at the Mitkof Island site. Logging appeared to affect the growth of steelhead fry and the abundance and distribu...

Effects of submarine mine tailings disposal on juvenile yellowfin sole (pleuronectes aspen): A laboratory study

Behaviour, survival, and growth studies were conducted in the laboratory on juvenile yellowfin sole (Pleuronectes asper) exposed to mine tailings produced by a pilot plant for a gold mine near Juneau, Alaska. Fish avoided fresh tailings in favour of natural marine sediment (control) and weathered tailings (75 years old). Only when fresh tailings were covered with 2 cm of control sediment did fish prefer control and fresh tailings equally. Survival of fish was similar (p = 0.66) for fish held on all test sediments. Fish held on fresh tailings for 60 d grew significantly (p = 0.013) less than control fish during the first, but not the second, month. Avoidance or short-term reductions in flatfish growth may occur from submarine disposal of tailings. Rapid burial of tailings in areas with high natural sedimentation (e.g., large river mouths) may accelerate recovery of the sea floor.

Retention of Jet-Injected Marks on Juvenile Coho and Sockeye Salmon

Abstract Juvenile coho salmon Oncorhynchus kisutch and sockeye salmon O. nerka were marked by jet injection to determine mark retention of three substances: Alcian Blue dye, black india ink, and acrylic paint (red, fluorescent yellow, and fluorescent orange). Fish were marked on the caudal fin and then held for 40 weeks in flow-through freshwater tanks. Coho and sockeye salmon both retained Alcian Blue and fluorescent orange marks best. The highest mark retention after 40 weeks was 73% for Alcian Blue marks on sockeye salmon. Overall mark retention was greater for orange-, yellow-, and black-marked coho salmon than for similarly marked sockeye salmon. Differences in growth rate—sockeye salmon grew about 7 mm more than coho salmon—probably contributed to the differences in mark retention between species. All colors appear suitable for short-term ( 6 weeks) marks, we recommend Alcian Blue dye or fluorescent orange or yellow acrylic paint for coho salmon and Alcian Blue dye fo...

Fish Assemblages in Shallow, Nearshore Habitats of the Bering Sea

Abstract The Bering Sea provides over one-half of U.S. fishery production, yet knowledge of the use of its shallow (<5 m), nearshore (<20 m from shore) waters by fish is limited. In June 2005, we sampled shallow, nearshore waters of the Bering Sea at three Aleutian islands with a beach seine to estimate the relative abundance and species distribution of fish. Three habitat types were sampled: Nonvegetated sand substrate, vegetated cobble substrate, and vegetated bedrock substrate. A total of 70 sites were seined on Akutan, Akun, and Unalaska islands. The total estimated catch was 83,910 fish representing 33 taxa. Five species comprised 98% of the total catch. Pacific sand lance Ammodytes hexapterus was the most abundant species; approximately 35,000 of these fish were captured, and they occurred in 60% of all seine hauls. The next most abundant fish were young-of-the-year (age-0) gadids (primarily walleye pollock Theragra chalcogramma), age-0 pink salmon Oncorhynchus gorbuscha, age-0 Pacific sandfish Tric...

Deposition, fate, and characteristics of derelict trawl web on an Alaskan beach

Abstract Derelict trawl web washed ashore on an 8 km beach near Yakutat, Alaska was counted, weighed, measured for mesh size, and tagged periodically from September 1985 to September 1987 to determine deposition rate, fate, and net characteristics. Approximately nine fragments of trawl web were deposited per km of beach per year. Significantly more fragments were washed ashore during the fall and winter than during the spring and summer. A total of 165 fragments of trawl web were tagged of which 72 (44%) were recovered during the last survey in September 1987; most (73%) fragments recovered remained near their original tagging location. Fragments not recovered probably were either washed inland or buried by sand during storms. The average weight of a fragment of trawl web was 4.0 kg and one-third of the fragments sampled had mesh sizes (≥ 15 cm) with the potential, while adrift at sea, to entangle northern fur seals.

Fate of radio-tagged trawl web on an Alaskan beach

Thirty-five fragments of trawl web were radio-tagged on Kayak Island, Alaska, to determine their fate once stranded ashore. Tagged fragments placed in the immediate study area were monitored daily by a remote tracking station (RTS) from August 1994 to May 1995. Ground and aerial surveys in June 1995 located fragments that had moved out of the reception range of the RTS. Of the 35 tagged fragments, 18 (51%) remained on Kayak Island, whereas the whereabouts of 17 (49%) fragments were undetermined. Most fragments not relocated were lost during severe fall storms. Tagged fragments that remained on Kayak Island moved an average of 2.0 km from their original tagging location. Fragments not relocated were smaller (x = 1.25 kg) than those found (x = 6.28 kg). Missing fragments were likely washed back to sea. To reduce entanglement hazards to marine life, stranded trawl web should be removed from beaches during clean-ups to prevent possible reentry into the ocean.

Diel differences in fish assemblages in nearshore eelgrass and kelp habitats in Prince William Sound, Alaska

The importance of a particular habitat to nearshore fishes can be best assessed by both diurnal and nocturnal sampling. To determine diel differences in fish assemblages in nearshore eelgrass and understory kelp habitats, fishes were sampled diurnally and nocturnally at six locations in western Prince William Sound, Alaska, in summer 2007. Abundance of fish between day and night were similar, but species composition and mean size of some fish changed. Species richness and species diversity were similar in eelgrass during the day and night, whereas in kelp, species richness and species diversity were greater at night than during the day. In eelgrass, saffron cod (Eleginus gracilis) was the most abundant species during the day and night. In kelp, the most abundant species were Pacific herring (Clupea pallasii) during the day and saffron cod at night. Diel differences in fish size varied by species and habitat. Mean length of saffron cod was similar between day and night in eelgrass but was greatest during the day in kelp. Pacific herring were larger at night than during the day in kelp. Diel sampling is important to identity nearshore habitats essential to fish and help manage fish stocks at risk.