Effect of temperature and tissue type on fatty acid signatures of two species of North Pacific juvenile gadids: A laboratory feeding study

The utility of the fatty acid biomarker (FAB) approach in fisheries ecology is limited by our understanding of how biotic and abiotic factors determine dietary markers in fish tissues. An 8-week laboratory experiment was conducted on two species of juvenile gadids (Pacific cod, Gadus macrocephalus and walleye Pollock, Theragra chalcogramma) reared at 3 °C or 9 °C and fed a diet enriched with either oils of marine origin or terrestrial plant origin. Non-linear models were fitted to investigate how tissue type and temperature mediated the proportion of FABs in fish. Across temperatures, fatty acid (FA) profiles were similar for both species of gadids. FAs also showed high temporal sensitivity across temperatures, and were evident in fish after only one week of feeding. Pacific cod held at 9 °C and fed a terrestrial plant oil (TPO) enriched diet had significantly higher C₁₈ polyunsaturated FAs (PUFAs) in their liver than cod held at 3 °C after one week, but this temperature effect diminished as tissues reached equilibrium with their diet. C₁₈ PUFAs were significantly higher in liver than in muscle.Differential proportions of C₁₈ PUFAs among tissues provide temporal patterns that may help with disentangling the timing of offshore– inshore nursery migrations in juvenile fish. Calibration coefficients were determined to explain the relationship between FAs in the diet and FAs in fish tissues. These coefficients will support future development of quantitative estimates of diet in juvenile low-fat fish.Keywords: Juvenile, Cod, Pollock, Fatty acid, Biomarker, Temperatur

Role of temperature on lipid/fatty acid composition in Pacific cod (Gadus macrocephalus) eggs and unfed larvae

During early development, oviparous fish species must use finite lipid and fatty acid (FA) reserves for both catabolism and structural components. In cold environments, developing fish have the additional constraint of maintaining membrane fluidity for metabolic efficiency (homeoviscous adaptation), resulting in further demand on lower melting point FAs like n-3 polyunsaturated fatty acids (PUFAs). To examine whether marine fish embryos physiologically adapt to changing temperature environments, we incubated Pacific cod (Gadus macrocephalus) eggs at 5 temperatures (0, 2, 4, 6, and 8 °C) in the laboratory and sampled them repeatedly during development to measure changes in lipid/FA composition. Pacific cod embryos increased n-3 PUFA content during the egg stage in all temperature treatments, with the possible exception of 0 °C, where poor survival and hatch success limited our ability for continued sampling. At the beginning of the hatch cycle, free-swimming embryos shifted from lipogenesis to lipid catabolism. The rates of lipogenesis and catabolism were temperature dependent, and the distinct increase in unsaturated fatty acids at temperatures <8 °C was consistent with homeoviscous adaptation theory. However, with the possible exception of embryos at 0 °C, the relative amounts of essential fatty acids (e.g., EPA, DHA, AA) were conserved in a similar manner across incubation temperatures. Collectively, these data suggest Pacific cod are capable of homeoviscous adaptation but cannot tolerate temperatures approaching 0 °C despite their possible ability to biosynthesize PUFAs from other energetic sources

Temperature-dependent growth and behavior of juvenile Arctic cod (Boreogadus saida) and co-occurring North Pacific gadids

The thermal sensitivity of Arctic fish species is poorly understood, yet such data are a critical component of forecasting and understanding ecosystem impacts of climate change. In this study, we experimentally measured temperature-dependent growth and routine swim activity in the juvenile stage of two Arctic gadids (Arctic cod, Boreogadus saida and saffron cod, Eleginus gracilis) and two North Pacific gadids (walleye pollock, Gadus chalcogrammus and Pacific cod, Gadus macrocephalus) over a 6-week growth period across five temperatures (0, 5, 9, 16 and 20°C). Arctic cod demonstrated a cold-water, stenothermic response in that there was relatively high growth at 0°C (0.73 % day⁻¹), near-maximal growth at 5°C (1.35 % day⁻¹) and negative impacts on activity, growth and survival at 16 °C. In contrast, saffron cod demonstrated a warmer-water, eurythermic response, and temperature had a positive effect on growth and condition beyond 16°C. However, despite these distinct thermal responses, walleye pollock and Pacific cod grew 2–3 times faster than Arctic gadids across a relatively broad temperature range above 5°C. These results, coupled with possible northward expansion by both Pacific cod and walleye pollock, suggest Arctic cod are highly vulnerable to continued climate change in the Arctic, especially in coastal areas of the Beaufort and Chukchi Seas where temperatures already exceed 14°C in the summer growth period.This is the publisher’s final pdf. The article is copyrighted by the US Government and published by Springer. It can be found at: http://link.springer.com/journal/300Keywords: Climate change, Saffron cod, Walleye pollock, Thermal sensitivity, Pacific cod, Biogeograph

Total Lipids, Lipid Classes, and Fatty Acids of Newly Settled Red King Crab (Paralithodes camtschaticus): Comparison of hatchery-cultured and wild crabs

Little is known about the nutrition or lipid metabolism of cold-water crabs, particularly in the North Pacific. We undertook a 2-part study to understand more completely the energetics and nutritional requirements of juvenile red king crab (RKC; Paralithodes canusehaticus). First, we investigated changes in proximate composition, total lipids (TLs), lipid classes, and fatty acids (FAs) throughout a molt cycle (C4-C5). Trends in lipid parameters were described by a 3-pari, piecewise linear regression with 3 distinct stages: (I) a postmolt phase (similar to 0-7 days), (2) an intramolt stage (similar to 7-24 days), and (3) a premolt stage (similar to 24-33 days). Significant intramolt differences in TLs indicated that caution should be taken when comparing crabs of unknown molt stage in future aquaculture and ecological experiments. However, little variability was found in the proportional FA composition of crabs, indicating that the intramolt stage has little effect on the interpretation of FA biomarkers. During a second investigation, we examined differences in lipid classes and FAs from cultured and wild RKC. We found significantly higher proportions of the essential fatty acids (EFAs) 20:5n-3 (EPA) and 20:4n-6 (AA) in wild crabs compared with cultured animals at the same stage. Furthermore, higher proportions of bacterial markers and lower proportions of zooplankton FA markers were found in wild than in hatchery-reared crabs. Here, we provide the first baseline data for future dietary studies on juvenile cold-water crabs. We suggest that an initial EFA ratio for DHA:EPA:AA of 5:8:1 could be used as a starting point for controlled dietary studies on the effect of EFAs on juvenile growth, molt success, and survival.Keywords: Lipids, Nutrition, Red king crab, Paralithodes camtschaticus, Fatty acids, Mol

Ontogenetic and spatial variability in trophic biomarkers of juvenile saffron cod (Eleginus gracilis) from the Beaufort, Chukchi and Bering Seas

Climate models indicate the Arctic will undergo dramatic environmental change with forecasted increases in temperature and river runoff. Saffron cod (Eleginus gracilis) is abundant in nearshore waters and appears in the diet of many Arctic sea birds and marine mammals; however, little is known about its early ecology and consequently how they might be affected by environmental changes. We aimed to characterize the mechanisms of spatial and ontogenetic variation in trophic biomarkers (lipid classes, fatty acids and bulk C and N stable isotopes) of saffron cod from the Western Arctic, Chukchi and Bering Seas. Size-standardized analyses showed a significant difference in lipid condition metrics and trophic biomarkers as a function of survey location. Both ontogeny and sampling location played an important role in determining lipid stores with elevated levels in both small offshore juveniles (75 mm). Higher lipid storage in Arctic juveniles was associated with elevated levels of diatom fatty acid markers, but not with nearshore carbon input. Increased lipids were found in age-1 juveniles from Prudhoe Bay in the Western Beaufort that were feeding at a lower trophic level than similarly sized age-0 juveniles from surface trawls in the Bering Sea. The use of otolith annuli revealed two discrete patterns of growth that help explain the trade-offs between energy storage and rapid growth that diverge between the Arctic and Bering Sea. Laboratory temperature-growth experiments confirmed that saffron cod have a eurythermal growth response and are able to store excess lipids at temperatures as high as 20°C.Keywords: Arctic, Nutrition, Fatty acids, Saffron cod, Lipids, OntogenyKeywords: Arctic, Nutrition, Fatty acids, Saffron cod, Lipids, Ontogen

CopemanLouiseHMSCEffectTemperatureTissueSupplementalMaterial.pdf

The utility of the fatty acid biomarker (FAB) approach in fisheries ecology is limited by our understanding of how biotic and abiotic factors determine dietary markers in fish tissues. An 8-week laboratory experiment was conducted on two species of juvenile gadids (Pacific cod, Gadus macrocephalus and walleye Pollock, Theragra chalcogramma) reared at 3 °C or 9 °C and fed a diet enriched with either oils of marine origin or terrestrial plant origin. Non-linear models were fitted to investigate how tissue type and temperature mediated the proportion of FABs in fish. Across temperatures, fatty acid (FA) profiles were similar for both species of gadids. FAs also showed high temporal sensitivity across temperatures, and were evident in fish after only one week of feeding. Pacific cod held at 9 °C and fed a terrestrial plant oil (TPO) enriched diet had significantly higher C₁₈ polyunsaturated FAs (PUFAs) in their liver than cod held at 3 °C after one week, but this temperature effect diminished as tissues reached equilibrium with their diet. C₁₈ PUFAs were significantly higher in liver than in muscle.Differential proportions of C₁₈ PUFAs among tissues provide temporal patterns that may help with disentangling the timing of offshore– inshore nursery migrations in juvenile fish. Calibration coefficients were determined to explain the relationship between FAs in the diet and FAs in fish tissues. These coefficients will support future development of quantitative estimates of diet in juvenile low-fat fish.Keywords: Biomarker, Cod, Fatty acid, Pollock, Juvenile, Temperatur

Molting, growth, and energetics of newly-settled blue king crab: Effects of temperature and comparisons with red king crab

Populations of blue king crab (BKC) (Paralithodes platypus Brandt, 1850) have declined in Alaskan waters over recent decades, and substantial effort is being made to rehabilitate the once important fishery with releases of hatchery-reared juveniles. However, little is known about the species' first year of post-settlement life. This study was conducted to evaluate how temperature mediates growth and energy allocation beginning with the first benthic instar (stage C1). Juvenile BKC were reared in four temperatures (1.5 to 12 °C) for a period of 60 days in low-density populations (150 crabs m⁻²) and 120 days in individual cultures. Growth rate increased rapidly up to 8 °C, and then leveled off. At 60 days, most of the crabs in 1.5 °C remained at stage C1, most in 4.5 °C were C2, and most in 8 °C were C3, while those in 12 °C were highly variable and ranged from C2 to C5. Growth records for individuals revealed an inverse exponential relationship between water temperature and intermolt period (up to 8 °C). A small decrease in molt increment at 12 °C resulted in crabs 6% smaller than those at 8 °C. Total lipid content increased with temperature in C2 BKC, but the response was variable and not significant in later stages. The proportion of storage class lipids (triacylglycerols) increased with an increase in temperature and polar lipids decreased. Concentrations of essential fatty acids were relatively constant over all temperature treatments, indicating that temperature and growth rate did not affect the biochemical condition of juvenile BKC. Survival rates of BKC (>95%) were similar across temperatures and were much higher than rates observed for red king crab (RKC) (Paralithodes camchaticus Tilesius 1815) (65–72%) in identical experiments. Growth rates of the two species were nearly identical up to 8 °C, but RKC grew faster than BKC at temperatures greater than 8 °C, with more molts resulting in larger individuals. Fatty acid (FA) signatures supported the lipid class data and showed that BKC had higher proportions of FA associated with energy storage while RKC had higher proportions of polyunsaturated FAs associated with membranes. These results indicate that BKC are the hardier species, and it shows little sign of cannibalism in culture (unlike RKC), but RKC grow faster at high temperature and are less vulnerable to warming climate. These data help to model temperature-dependent recruitment processes in the field and assist in the design of diets and hatchery conditions for production of seed stocks intended for field release.Keywords: Lipid, Paralithodes platypus, Bioenergetics, Fatty acid, Temperature, Culture, Growt

CopemanLouiseHMSCEffectTemperatureTissue.pdf

The utility of the fatty acid biomarker (FAB) approach in fisheries ecology is limited by our understanding of how biotic and abiotic factors determine dietary markers in fish tissues. An 8-week laboratory experiment was conducted on two species of juvenile gadids (Pacific cod, Gadus macrocephalus and walleye Pollock, Theragra chalcogramma) reared at 3 °C or 9 °C and fed a diet enriched with either oils of marine origin or terrestrial plant origin. Non-linear models were fitted to investigate how tissue type and temperature mediated the proportion of FABs in fish. Across temperatures, fatty acid (FA) profiles were similar for both species of gadids. FAs also showed high temporal sensitivity across temperatures, and were evident in fish after only one week of feeding. Pacific cod held at 9 °C and fed a terrestrial plant oil (TPO) enriched diet had significantly higher C₁₈ polyunsaturated FAs (PUFAs) in their liver than cod held at 3 °C after one week, but this temperature effect diminished as tissues reached equilibrium with their diet. C₁₈ PUFAs were significantly higher in liver than in muscle.Differential proportions of C₁₈ PUFAs among tissues provide temporal patterns that may help with disentangling the timing of offshore– inshore nursery migrations in juvenile fish. Calibration coefficients were determined to explain the relationship between FAs in the diet and FAs in fish tissues. These coefficients will support future development of quantitative estimates of diet in juvenile low-fat fish.Keywords: Pollock, Cod, Biomarker, Temperature, Juvenile, Fatty acidKeywords: Pollock, Cod, Biomarker, Temperature, Juvenile, Fatty aci

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