Juvenile Steelhead Distribution, Migration, Feeding, and Growth in the Columbia River Estuary, Plume, and Coastal Waters

Figures & data

Table 1 Numbers of juvenile steelhead that were sampled in marine waters off the coasts of Oregon and Washington during annual May surveys. Counts of steelhead were adjusted by the annual rate of hatchery marking to estimate the numbers of unmarked fish and hatchery fish.

Year	Hatchery marking rate (%)	Adjusted number of naturally produced fish	Adjusted number of hatchery fish	Total number of fish sampled
2000	82.0	5	2	7^a
2001	73.0	23	79	102^a
2002	79.2	21	75	96^a
2003	79.5	2	1	3^a
2004	80.5	3	30	33^a
2005	86.0	0	0	0^a
2006	82.7	45	247	292^a
2007	83.9	23	22	45^a
2008	80.4	26	48	74^a
2009	79.8	11	32	43^a
2010	82.1	16	30	46^a
2011	87.8	14	25	39^a

^aIncludes special study fish that were collected in May of 2001 and 2002 (De Robertis et al. 2005).

FIGURE 1 Average CPUE (fish/km towed) for hatchery (circles) and unmarked (triangles) juvenile steelhead at each station sampled during National Oceanic and Atmospheric Administration Fisheries’ pelagic trawl surveys in (a) May (1999 and 2006–2011, when broad surveys occurred) and (b) June (1998–2011). The 100- and 200-m isobath lines are shown in light gray.

FIGURE 2. Annual maps of station CPUE (fish/km towed) for juvenile steelhead collected during National Oceanic and Atmospheric Administration Fisheries’ pelagic trawl surveys off the coasts of Washington and Oregon in 1999–2011. No fish were captured in 1999 or 2005. The numbers of fish captured each year (n) are shown. In 2001 and 2002, additional samples were obtained during a supplemental study near the Columbia River plume front (De Robertis et al. 2005); sample sizes from that study are shown in parentheses. The 100- and 200-m isobath lines are shown in light gray.

FIGURE 3. Log(x + 0.1)-transformed CPUE (fish/km towed) for juvenile steelhead presented in relation to the surface salinity (‰; at 1 m) measured at the sampling station. The station was considered to be (1) in surface plume waters when salinity at 1-m depth was less than 28‰ or (2) outside of plume waters when salinity was greater than 28‰.

Table 2 Release and recovery information for coded-wire-tagged or PIT-tagged steelhead that were caught in marine waters off the coasts of Washington and Oregon. The mid-Columbia subbasin encompasses locations below the confluence of the Columbia and Snake rivers, including the Willamette and Umatilla rivers; the upper Columbia subbasin includes all tributaries above the confluence of the Columbia and Snake rivers. The Snake River basin includes all tributaries to the Snake River.

Release basin or subbasin	n	Days at large	Release latitude	Recovery location transects^a
Columbia River
Mid-Columbia subbasin	5	23.4	46°15′N	Cape Meares, Columbia River, Willapa Bay
Upper Columbia subbasin	5	28.8	46°15′N	Columbia River
Snake River	37	41.1	46°15′N	Cape Meares, Columbia River, Willapa Bay, La Push
Washington coast
Quinault River	7	33.5^b	47°55’N	Columbia River, Grays Harbor, Queets River
Sooes River	1	23	48°19’N	Columbia River

^aRecovery location transects are illustrated in Figure 1. The Columbia River transect includes data from special studies that sampled juvenile steelhead near the mouth of the Columbia River.^bFor two of the steelhead tagged in the Quinault River, the date of release was not provided in the coded wire tag database. Therefore, the number of days at large describes only the five fish with release date information.

Table 3 Size, growth, and residence parameters calculated based on otolith structural and elemental data from 47 juvenile steelhead collected off the coasts of Washington and Oregon. Hatchery fish had adipose fin clips and/or coded wire tags.

Variable	n	Mean	SD	Min	Max
Hatchery steelhead
Size at freshwater emigration (FL, mm)	16	224.3	24.6	174	250.7
Marine growth (% per day, mm)	16	0.15	0.03	0.12	0.2
Marine growth (mm/d)	16	0.33	0.06	0.24	0.49
Size at capture (FL, mm)	36	229.4	21.54	178	259.8
Day of capture	36	145.6	1.9	144	150
Marine residence period (d)	36	9.9	10.5	3	33
Day of freshwater emigration	36	135.63	10.1	112	147
Unmarked steelhead
Size at freshwater emigration (FL, mm)	5	211.4	46.3	134	252.1
Marine growth (% per day, mm)	5	0.14	0.03	0.1	0.17
Marine growth (mm/d)	5	0.3	0.09	0.21	0.4
Size at capture (FL, mm)	11	212.7	34.3	137.2	264.9
Day of capture	11	146	2.1	144	150
Marine residence period (d)	11	9.4	9.8	3	32.2
Day of freshwater emigration	11	136.7	8	117.8	143

FIGURE 4. Composition of the diet consumed by juvenile steelhead off the coasts of Oregon and Washington, 2000–2011. Fish prey taxa are shown in color, whereas other taxa are shown in grayscale. The “other” category includes arachnids, cirripedes (barnacle larvae), mysids, polychaetes, isopods, and gelatinous material. The “other teleosts” category includes clupeids, gadids, salmonids, osmerids, and other unidentified fish (including fish tissue and parts). Unidentified crustacean parts and material, fish scales, unidentified material, plant material, and plastic were excluded from the analysis. See Appendix Table A.1 for common names of taxa.

FIGURE 5. Cluster analysis using the similarity profile (SIMPROF) procedure, which identified three groupings of yearly average diets for juvenile steelhead collected off the coasts of Washington and Oregon.

FIGURE 6. Annual means (±SE) of feeding intensity (weight of prey expressed as a percentage of total body weight) for hatchery (marked; filled circles) and unmarked (open circles) steelhead sampled in the ocean off the coasts of Oregon and Washington (main panel) and in the Columbia River estuary (inset) from 2000 to 2011. Horizontal lines are the overall means across all years for marked steelhead and unmarked fish. An asterisk indicates a significant difference between marked and unmarked fish in that year and habitat. Ocean data are not shown for 2003 or 2005 because too few fish were captured during those years.

FIGURE 7. Annual means (±SE) of (a) FL, (b) body condition residual (condition index), and (c) insulin-like growth factor 1 (IGF-1) for hatchery (marked; filled circles) and unmarked (open circles) steelhead caught in the ocean (main panels) or in the Columbia River estuary (insets). Horizontal lines are the overall means across years for hatchery steelhead and unmarked fish. An asterisk indicates a significant difference between hatchery and unmarked fish in that year and habitat; “n/a” means that too few data were available to test for significance.

Table 4 Biological characteristics of ocean-caught juvenile steelhead in relation to capture distance from shore averaged in 8-km blocks. For each biological characteristic (FL, condition index, etc.), we tested for differences between 8-km blocks; for a given variable, values without a letter in common were significantly different (ANOVA: P < 0.05). No significant among-block differences in FL or insulin-like growth factor 1 (IGF-1) were found for unmarked fish.

	Distance from shore (8-km blocks)
Variable	8 km	16 km	24 km	32 km	40 km	48 km
Hatchery steelhead
FL (mm)	212.47 zyx	216.17 z	218.71 zy	222.28 x	224.92 z	232.17 yx
Condition residual	−0.0337 zy	−0.0358 z	−0.0077 yx	−0.02 zy	−0.0074 yx	0.0243 x
IGF-1 (ng/mL)	41.3 z	46.7 zy	52.1 yx	54.5 x	54.2 x	68.4 w
Stomach fullness (%)	0.29 z	0.48 zy	0.62 yx	0.74 x	1.0 w	1.03 w
Unmarked steelhead
FL (mm)	186.8462	201.7222	208.3333	213.7451	215.0244	217
Condition residual	−0.027 z	−0.002 z	0.049 y	0.066 y	0.013 z	0.062 y
IGF-1 (ng/mL)	43.7816	53.238	55.342	60.2274	55.8742	61.3537
Stomach fullness (%)	0.28 z	0.75 zy	1.5 zyx	1.3 x	1.6 yx	1.16 x

FIGURE 8. Means (±SE) for the relationship between capture site distance from shore (km) and the (a) mean FL, (b) body condition residual (condition index), (c) insulin-like growth factor 1 (IGF-1), and (d) percent feeding intensity for hatchery (filled circles) and unmarked (open circles) steelhead juveniles. Distances offshore were rounded to the nearest 8-km station for ease of visualizing the patterns. Sample sizes of hatchery and unmarked fish are shown above or below the symbols.

Table

Prey taxon	FO (%)	N (%)	W (%)
Annelida
Unidentified Polychaeta*	0.50	0.08	0.27
Mollusca
Gastropoda:
Sea butterfly Limacina helicina*	1.45	23.28	4.69
Unidentified Pteropoda*	0.20	0.30	0.26
Arthropoda
Copepoda:
Neocalanus cristatus	0.05	0.32	0.02
Unidentified Calanoida	0.35	1.76	0.44
Unidentified Copepoda	0.65	0.41	0.09
Cirripedia:
Unidentified Cirripedia	0.15	3.48	0.04
Gooseneck barnacles Lepas spp.	0.15	3.48	0.04
Mysidacea:
Unidentified Mysidacea	0.10	0.02	0.01
Isopoda:
Idotea spp.	0.05	0.01	0.00
Idotea fewkesi	0.05	0.02	0.06
Unidentified Isopoda*	0.15	0.02	0.01
Amphipoda:
Atylus tridens	1.50	0.44	0.19
Americorophium spp.*	0.10	0.02	0.00
Unidentified Gammaridae*	1.80	0.76	0.15
Brachyscelus crusculum	0.05	0.02	0.03
Hyperia medusarum	0.35	0.12	0.08
Hyperoche medusarum	3.95	1.84	0.37
Lycaea pulex	0.15	0.02	0.00
Primno macropa	0.15	0.04	0.02
Themisto pacifica	0.15	0.03	0.00
Vibilia spp.	0.05	0.01	0.00
Vibilia australis	0.05	0.49	0.03
Vibilia pyripes	0.15	0.31	0.05
Unidentified Hyperiidea	4.85	1.78	0.61
Unidentified Amphipoda	0.05	0.04	0.01
Euphausiacea (krill):
Euphausia pacifica	5.55	4.53	7.27
Thysanoessa spinifera	4.40	1.65	4.07
Unidentified Euphausiacea*	10.65	7.26	8.99
Decapoda:
Unidentified Brachyura zoeae	0.20	0.08	0.00
Crab Cancer spp. megalopae	2.70	1.06	0.92
Dungeness crab Cancer magister megalopae	10.25	8.04	8.47
Pygmy rock crab Cancer oregonensis/red rock crab Cancer productus megalopae	3.15	1.07	0.40
Unidentified Pandalidae	0.15	0.02	0.00
Unidentified Decapoda	1.30	0.45	0.41
Insecta:
Aphidae	0.05	0.01	0.01
Coleoptera*	0.65	0.14	0.09
Diptera*	0.15	0.03	0.00
Hymenoptera	0.15	0.06	0.04
Homoptera	0.05	0.01	0.02
Unidentified Insecta*	5.45	1.28	0.83
Arachnida:
Unidentified Araneae (spiders)	0.05	0.01	0.00
Unidentified Arachnida*	0.05	0.01	0.00
Chordata
Osteichthyes:
Unidentified Clupeidae	0.10	0.02	0.05
Chum Salmon Oncorhynchus keta	0.05	0.02	0.80
Unidentified Osmeridae	0.05	0.02	0.06
Pacific Tomcod Microgadus proximus	0.05	0.01	0.06
Pacific Saury Cololabis saira	0.05	0.01	0.06
Pacific Sand Lance Ammodytes hexapterus	1.55	0.65	3.35
Rockfishes Sebastes spp.	3.45	1.33	12.02
Sablefish Anoplopoma fimbria	2.35	2.38	5.94
Kelp Greenling Hexagrammos decagrammus	0.85	0.24	3.36
Lingcod Ophiodon elongatus	0.20	0.06	0.48
Unidentified Hexagrammidae	1.00	0.30	3.45
Irish lords Hemilepidotus spp.	0.80	0.27	0.97
Brown Irish Lord Hemilepidotus spinosus	0.50	0.14	0.61
Cabezon Scorpaenichthys marmoratus	0.65	0.15	0.61
Unidentified Cottidae	1.35	0.53	1.16
Unidentified Pleuronectidae	0.10	0.02	0.07
Unidentified Osteichthyes*	14.86	6.50	22.28
Gelatinous material	0.10	0.05	0.02
Number of stomachs examined		671
Number of empty stomachs		30
Mean FL (mm)		216.7
FL range (mm)		138–290

De Robertis, A., C.A. Morgan, R.A. Schabetsberger, R.W. Zabel, R.D. Brodeur, R.L. Emmett, C.M. Knight, G.K. Krutzikowsky, and E. Casillas. 2005. Columbia River plume fronts II. Distribution, abundance, and feeding ecology of juvenile salmon. Marine Ecology Progress Series 299:33–44.

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