Fatty acids (FA) represent a large group of molecules that comprise the majority of lipids found in all organisms. Their great diversity, biochemical restrictions and, in some cases, unique origin among plants and animals has fostered a number of areas of research, ranging from assessment of animal nutrition and metabolism, to investigating trophic interactions and ecosystem structure. Over the past three decades, we have observed the use of FA develop from a potential tool for delineating food webs (Ackman and Eaton 1966) to a powerful technique for quantitative assessment of predator diets . Studies that have compared the FA found in predator fat stores with those found in their prey have allowed both qualitative (e

Problem statement: Spoilage of food products is due to chemical, enzymatic or microbial activities One-fourth of the worlds food supply and 30% of landed fish are lost through microbial activity alone. With the ever growing world population and the need to store and transport the food from one place to another where it is needed, food preservation becomes necessary in order to increase its shelf life and maintain its nutritional value, texture and flavor. The freshness and quality of fish have always gained the attention by Food Regulatory Agencies and Food Processing Industry. Proper handling, pretreatment and preservation techniques can improve the quality fish and fish products and increase their shelf life. Methodology: Historically salting, drying, smoking, fermentation and canning were the methods to prevent fish spoilage and extend its shelf life. In response to consumer demand for texture, appearance and taste, new methods were developed including: Cooling, freezing and chemical preservation. A comprehensive review of the literature on the subject of fish spoilage and modern preservation techniques was carried out. Conclusion: Fish spoilage results from three basic mechanisms: Enzymatic autolysis, oxidation, microbial growth. Low temperature storage and chemical techniques for controlling water activity, enzymatic, oxidative and microbial spoilage are the most common in the industry today. A process involving the addition of an EDTA (1 mM)-TBHQ (0.02%) combination and ascorbic acid and storage at refrigerated temperatures (5°C) in darkness can be the most positive for controlling the spoilage of fish and fish product. The suggested process would address antimicrobial activity as well as destructive oxidation of the desired lipids and fats. However, more efforts are required to understand the role of proximate composition of fish, post harvest history, environmental conditions, initial microbial load, type and nature of bacteria and their interaction in order to optimize the shelf-life of fish

Global warming and the loss of sea ice threaten to alter patterns of productivity in arctic marine ecosystems because of a likely decline in primary productivity by sea ice algae. Estimates of the contribution of ice algae to total primary production range widely, from just 3 to[50%, and the importance of ice algae to higher trophic levels remains unknown. To help answer this question, we investigated a novel approach to food web studies by combining the two established methods of stable isotope analysis and fatty acid (FA) analysis-we determined the C isotopic composition of individual diatom FA and traced these biomarkers in consumers. Samples were collected near Barrow, Alaska and included ice algae, pelagic phytoplankton, zooplankton, fish, seabirds, pinnipeds and cetaceans. Ice algae and pelagic phytoplankton had distinctive overall FA signatures and clear differences in d 13 C for two specific diatom FA biomarkers: 16:4n-1 (-24.0 ± 2.4 and -30.7 ± 0.8%, respectively) and 20:5n-3 (-18.3 ± 2.0 and -26.9 ± 0.7%, respectively). Nearly all d 13 C values of these two FA in consumers fell between the two stable isotopic end members. A mass balance equation indicated that FA material derived from ice algae, compared to pelagic diatoms, averaged 71% (44-107%) in consumers based on d 13 C values of 16:4n-1, but only 24% (0-61%) based on 20:5n-3. Our estimates derived from 16:4n-1, which is produced only by diatoms, probably best represented the contribution of ice algae relative to pelagic diatoms. However, many types of algae produce 20:5n-3, so the lower value derived from it likely represented a more realistic estimate of the proportion of ice algae material relative to all other types of phytoplankton. These preliminary results demonstrate the potential value of compound-specific isotope analysis of marine lipids to trace C flow through marine food webs and provide a foundation for future work.

Polar bears (Ursus maritimus) have experienced substantial changes in the seasonal availability of sea ice habitat in parts of their range, including the Beaufort, Chukchi, and Bering Seas. In this study, we compared the body size, condition, and recruitment of polar bears captured in the Chukchi and Bering Seas (CS) between two periods (1986-1994 and 2008-2011) when declines in sea ice habitat occurred. In addition, we compared metrics for the CS population 2008-2011 with those of the adjacent southern Beaufort Sea (SB) population where loss in sea ice habitat has been associated with declines in body condition, size, recruitment, and survival. We evaluated how variation in body condition and recruitment were related to feeding ecology. Comparing habitat conditions between populations, there were twice as many reduced ice days over continental shelf waters per year during 2008-2011 in the SB than in the CS. CS polar bears were larger and in better condition, and appeared to have higher reproduction than SB bears. Although SB and CS bears had similar diets, twice as many bears were fasting in spring in the SB than in the CS. Between 1986-1994 and 2008-2011, body size, condition, and recruitment indices in the CS were not reduced despite a 44-day increase in the number of reduced ice days. Bears in the CS exhibited large body size, good body condition, and high indices of recruitment compared to most other populations measured to date. Higher biological productivity and prey availability in the CS relative to the SB, and a shorter recent history of reduced sea ice habitat, may explain the maintenance of condition and recruitment of CS bears. Geographic differences in the response of polar bears to climate change are relevant to range-wide forecasts for this and other ice-dependent species.

The fat and fatty acid compositions of 28 species of fish and invertebrates (n = 954) from the Scotian Shelf, Georges Bank, and the Gulf of St. Lawrence were determined. Discriminant analysis of the 16 most numerous species (n [Formula: see text] 18 each), using 17 major fatty acids, classified species with greater than 98% accuracy and grouped species into three general clusters (gadids, flatfish, and planktivores) with similar fatty acid compositions, and likely, similar diets. A number of species exhibited changes in fatty acid signatures with increasing size (multivariate analysis of variance), which corresponded with known dietary shifts reported from stomach contents analyses. Location effects were also observed among the three major geographical regions and were probably due to broad-scale variations in prey assemblages and phytoplankton composition in the northwestern Atlantic. Despite these effects, within-species variation was still substantially less than among-species variation. Thus, fatty acid signatures can be used to distinguish and characterize fish and invertebrate species in a given ecosystem, as well as to study finer-scale trophic interactions of these species. These data also have applications at higher trophic levels and will serve as a prey database for studying the diets of other fish and marine mammal predators using fatty acid signatures.