Association of Juvenile Salmon and Estuarine Fish with Intertidal Seagrass and Oyster Aquaculture Habitats in a Northeast Pacific Estuary

Structured estuarine habitats, such as salt marshes, seagrass beds, and oyster reefs, are recognized as critical nurseries for juvenile fish and crustaceans. Estuarine habitat usage by fish, including juvenile Pacific salmon Oncorhynchus spp., was characterized by sampling with a modified tow net in Willapa Bay, Washington, where 20% of the intertidal area is utilized for shellfish aquaculture and thus is difficult to sample with conventional gear. Our goal was to compare fish use of relatively undisturbed habitats (open mudflat, seagrass, and channel habitats) with the use of nearby oyster culture habitat. Although many species showed significant temporal and spatial trends within the estuary, only Shiner Perch Cymatogaster aggregata exhibited a significant association with habitat. Juveniles of three salmonid species exhibited few associations with the low intertidal habitats over which they were captured or in the prey types they consumed there. Chinook Salmon O. tshawytscha, likely hatchery-released ocean-type fish, were the most common salmonid captured, and they utilized low intertidal areas throughout the summer as their mean size increased from 85 to 100 mm FL. Diets consumed by these larger juvenile Chinook Salmon were not associated with benthic habitat but instead consisted primarily of (1) insects from nearby marsh or terrestrial habitats and (2) planktonic prey, like decapod larvae and tunicate larvaceans. Juvenile Coho Salmon O. kisutch and Chum Salmon O. keta were captured earlier (April and May) and fed on a slightly different suite of prey taxa, which were also primarily pelagic rather than associated with the intertidal benthos. Our findings suggest that in this relatively shallow coastal estuary, the role of benthic habitat is not closely linked to its value as a source of food for large juvenile salmon out-migrants utilizing the low intertidal areas where aquaculture occurs

Feeding ecology of juvenile rockfishes off Oregon and Washington based on stomach content and stable isotope analyses

The feeding habits of pelagic, juvenile rockfishes (Sebastes spp.) collected off Oregon in 2002, and Oregon and Washington in 2006, were examined using stomach content and stable isotope analyses. Sampling occurred along a series of transects across the shelf between Crescent City, California (Lat. 41°54.0′), and Newport, Oregon (Lat. 44°39.0′), in 2002, and off Willapa Bay, Washington (Lat. 46°40.0′), and the Columbia River, Oregon (Lat. 46°10.0′), in 2006. Species composition varied both years with distance from shore, but the predominant species were darkblotched (Sebastes crameri), canary (S. pinniger), yellowtail (2006 only; S. flavidus), and widow (S. entomelas) rockfishes. Stomach content analysis revealed that darkblotched rockfish had highly variable diets, and canary, yellowtail, and widow rockfishes exhibited a high degree of overlap in 2006. Multivariate analysis showed significant differences in diet based on distance from shore where caught, fish size, and species. Stable isotope analysis indicated that all species were feeding at about the same trophic level within each year, with a 1.5 ‰ difference in δ¹⁵N between years and regions. The difference in δ¹⁵N values may indicate a greater contribution of mesotrophic zooplankton such as euphausiids, hyperiid amphipods, and chaetognaths to fish diets in 2006. Depleted ¹³C values were indicative of diets based on primary production from a more offshore origin, suggesting that these rockfish had previously inhabited offshore waters. These results add to our understanding of some of the important environmental factors that affect young-of-the-year rockfishes during their pelagic phase

Identification of Burrowing Shrimp Food Sources Along an Estuarine Gradient Using Fatty Acid Analysis and Stable Isotope Ratios

Two species of burrowing shrimp occur in high densities in US West Coast estuaries, the ghost shrimp, Neotrypaea californiensis, and the blue mud shrimp, Upogebia pugettensis. Both species of shrimp are considered ecosystem engineers as they bioturbate and irrigate extensive galleries within the sediment. While their burrows comprise a dominant habitat type in west coast estuaries, little is known about these shrimps’ diet and their role in estuarine food webs. The primary goals of this study were to identify major components of burrowing shrimp diets and detect variation in these diets along an estuarine gradient using combined fatty acid (FA) and stable isotope (SI) analyses. Shrimp and potential food sources including eelgrass blades, epiphytes, Ulva, sedimentary particulate organic matter (SPOM), burrow walls, and particulate organic material (POM) were sampled at different locations within Yaquina Bay, Oregon in August 2012. Both SI and FA analyses indicated differences in food resources assimilated by shrimp along the estuarine gradient. SI values showed that diets for U. pugettensis consisted of carbon sources derived primarily from POM and SPOM, while POM and epiphytes were primary carbon sources for N. californiensis. Shrimp from lower estuarine sites had high levels of 16:1ω7 and 20:5ω3 FAs suggesting their diet is enriched with marine diatoms. Shrimp from upriver showed greater proportion of FA associated with dinoflagellates and terrestrial sources as indicated by a high percentage of C18 polyunsaturated FAs (PUFAs). This is the first study to evaluate diets of these two shrimp species using complimentary FA and SI approaches

HosackGeoffreyFishWildlifeAssociationJuvenileSalmon(Supplement).pdf

Structured estuarine habitats, such as salt marshes, seagrass beds, and oyster reefs, are recognized as critical nurseries for juvenile fish and crustaceans. Estuarine habitat usage by fish, including juvenile Pacific salmon Oncorhynchus spp., was characterized by sampling with a modified tow net in Willapa Bay, Washington, where 20% of the intertidal area is utilized for shellfish aquaculture and thus is difficult to sample with conventional gear. Our goal was to compare fish use of relatively undisturbed habitats (open mudflat, seagrass, and channel habitats) with the use of nearby oyster culture habitat. Although many species showed significant temporal and spatial trends within the estuary, only Shiner Perch Cymatogaster aggregata exhibited a significant association with habitat. Juveniles of three salmonid species exhibited few associations with the low intertidal habitats over which they were captured or in the prey types they consumed there. Chinook Salmon O. tshawytscha, likely hatchery-released ocean-type fish, were the most common salmonid captured, and they utilized low intertidal areas throughout the summer as their mean size increased from 85 to 100 mm FL. Diets consumed by these larger juvenile Chinook Salmon were not associated with benthic habitat but instead consisted primarily of (1) insects from nearby marsh or terrestrial habitats and (2) planktonic prey, like decapod larvae and tunicate larvaceans. Juvenile Coho Salmon O. kisutch and Chum Salmon O. keta were captured earlier (April and May) and fed on a slightly different suite of prey taxa, which were also primarily pelagic rather than associated with the intertidal benthos. Our findings suggest that in this relatively shallow coastal estuary, the role of benthic habitat is not closely linked to its value as a source of food for large juvenile salmon out-migrants utilizing the low intertidal areas where aquaculture occurs

HosackGeoffreyFishWildlifeAssociationJuvenileSalmon.pdf

Structured estuarine habitats, such as salt marshes, seagrass beds, and oyster reefs, are recognized as critical nurseries for juvenile fish and crustaceans. Estuarine habitat usage by fish, including juvenile Pacific salmon Oncorhynchus spp., was characterized by sampling with a modified tow net in Willapa Bay, Washington, where 20% of the intertidal area is utilized for shellfish aquaculture and thus is difficult to sample with conventional gear. Our goal was to compare fish use of relatively undisturbed habitats (open mudflat, seagrass, and channel habitats) with the use of nearby oyster culture habitat. Although many species showed significant temporal and spatial trends within the estuary, only Shiner Perch Cymatogaster aggregata exhibited a significant association with habitat. Juveniles of three salmonid species exhibited few associations with the low intertidal habitats over which they were captured or in the prey types they consumed there. Chinook Salmon O. tshawytscha, likely hatchery-released ocean-type fish, were the most common salmonid captured, and they utilized low intertidal areas throughout the summer as their mean size increased from 85 to 100 mm FL. Diets consumed by these larger juvenile Chinook Salmon were not associated with benthic habitat but instead consisted primarily of (1) insects from nearby marsh or terrestrial habitats and (2) planktonic prey, like decapod larvae and tunicate larvaceans. Juvenile Coho Salmon O. kisutch and Chum Salmon O. keta were captured earlier (April and May) and fed on a slightly different suite of prey taxa, which were also primarily pelagic rather than associated with the intertidal benthos. Our findings suggest that in this relatively shallow coastal estuary, the role of benthic habitat is not closely linked to its value as a source of food for large juvenile salmon out-migrants utilizing the low intertidal areas where aquaculture occurs

Association of Juvenile Salmon and Estuarine Fish with Intertidal Seagrass and Oyster Aquaculture Habitats in a Northeast Pacific Estuary

<div><p></p><p>Structured estuarine habitats, such as salt marshes, seagrass beds, and oyster reefs, are recognized as critical nurseries for juvenile fish and crustaceans. Estuarine habitat usage by fish, including juvenile Pacific salmon <i>Oncorhynchus</i> spp., was characterized by sampling with a modified tow net in Willapa Bay, Washington, where 20% of the intertidal area is utilized for shellfish aquaculture and thus is difficult to sample with conventional gear. Our goal was to compare fish use of relatively undisturbed habitats (open mudflat, seagrass, and channel habitats) with the use of nearby oyster culture habitat. Although many species showed significant temporal and spatial trends within the estuary, only Shiner Perch <i>Cymatogaster aggregata</i> exhibited a significant association with habitat. Juveniles of three salmonid species exhibited few associations with the low intertidal habitats over which they were captured or in the prey types they consumed there. Chinook Salmon <i>O. tshawytscha</i>, likely hatchery-released ocean-type fish, were the most common salmonid captured, and they utilized low intertidal areas throughout the summer as their mean size increased from 85 to 100 mm FL. Diets consumed by these larger juvenile Chinook Salmon were not associated with benthic habitat but instead consisted primarily of (1) insects from nearby marsh or terrestrial habitats and (2) planktonic prey, like decapod larvae and tunicate larvaceans. Juvenile Coho Salmon <i>O. kisutch</i> and Chum Salmon <i>O. keta</i> were captured earlier (April and May) and fed on a slightly different suite of prey taxa, which were also primarily pelagic rather than associated with the intertidal benthos. Our findings suggest that in this relatively shallow coastal estuary, the role of benthic habitat is not closely linked to its value as a source of food for large juvenile salmon out-migrants utilizing the low intertidal areas where aquaculture occurs.</p><p>Received January 18, 2015; accepted May 19, 2015</p></div

Association of Juvenile Salmon and Estuarine Fish with Intertidal Seagrass and Oyster Aquaculture Habitats in a Northeast Pacific Estuary

<p>Structured estuarine habitats, such as salt marshes, seagrass beds, and oyster reefs, are recognized as critical nurseries for juvenile fish and crustaceans. Estuarine habitat usage by fish, including juvenile Pacific salmon <i>Oncorhynchus</i> spp., was characterized by sampling with a modified tow net in Willapa Bay, Washington, where 20% of the intertidal area is utilized for shellfish aquaculture and thus is difficult to sample with conventional gear. Our goal was to compare fish use of relatively undisturbed habitats (open mudflat, seagrass, and channel habitats) with the use of nearby oyster culture habitat. Although many species showed significant temporal and spatial trends within the estuary, only Shiner Perch <i>Cymatogaster aggregata</i> exhibited a significant association with habitat. Juveniles of three salmonid species exhibited few associations with the low intertidal habitats over which they were captured or in the prey types they consumed there. Chinook Salmon <i>O. tshawytscha</i>, likely hatchery-released ocean-type fish, were the most common salmonid captured, and they utilized low intertidal areas throughout the summer as their mean size increased from 85 to 100 mm FL. Diets consumed by these larger juvenile Chinook Salmon were not associated with benthic habitat but instead consisted primarily of (1) insects from nearby marsh or terrestrial habitats and (2) planktonic prey, like decapod larvae and tunicate larvaceans. Juvenile Coho Salmon <i>O. kisutch</i> and Chum Salmon <i>O. keta</i> were captured earlier (April and May) and fed on a slightly different suite of prey taxa, which were also primarily pelagic rather than associated with the intertidal benthos. Our findings suggest that in this relatively shallow coastal estuary, the role of benthic habitat is not closely linked to its value as a source of food for large juvenile salmon out-migrants utilizing the low intertidal areas where aquaculture occurs.</p> <p>Received January 18, 2015; accepted May 19, 2015</p