Elaboration of pâté using fish residues

Knowing the potential of fish waste for the preparation of pâtés, there is the possibility of adding greater sustainability to the aquaculture sector. The aim was to prepare pâtés from fish processing residues with the inclusion of smoked fishmeal and evaluate their sensory, microbiological, physicochemical, and shelf-life characteristics. Three treatments were used: pâté without fishmeal inclusion (PSF), with smoked salmon carcass meal inclusion (PFSD), and smoked tilapia carcass meal (PFTD). The inclusion of the flours reduced the moisture, carbohydrate, and water activity. However, they increased the ash, salt, and collagen content. The lipid content was higher for the PFSD. The PSF showed peak oxidation at 15 days and the PFSD and PFTD around 45 days over the course of the 90-day shelf-life. The luminosity and b* coordinate were lower for PFTD, while the a* coordinate was higher for PFSD. Only the b* coordinate showed changes in PSF and PFSD throughout the 30 days of shelf-life, and its color tended to yellow at 15 days. The sensory analysis did not differ statistically between treatments (p > 0.05) for all attributes, except color, where the highest score was attributed to PSF. As for the overall impression, PSF also obtained the highest score, which may be associated with its color. By including fish flours, the nutritional composition and color of the tilapia-trimmed pâtés are changed, achieving an average acceptance level of 67%.

Ideal free eagles: Bald Eagle distribution in relation to salmon availability on four salmon spawning rivers

The movement of individuals according to the availability of resources has a fundamental effect on animal distributions. In the Pacific Northwest, Bald Eagles (Haliaeetus leucocephalus (Linneaus, 1766)) rely heavily on scavenging opportunities during the non-breeding period, and their distribution and movements are thought to be strongly influenced by the availability of post-spawning Pacific salmon (genus Oncorhynchus Suckley, 1861) carcasses. We surveyed the abundance of eagles and salmon on four adjacent rivers on Vancouver Island, British Columbia, Canada, during the 2017 fall spawning season. Salmon began to arrive in late September, peaked in abundance in mid-November, and were absent after early December. The seasonal progression of Bald Eagle abundance matched that of salmon carcass availability. The slope of proportional eagle – salmon relationship was significantly positive, though lower than the 1:1 match predicted by Ideal Free Distribution theory. The numerical response of Bald Eagles to salmon abundance was elevated on one of the rivers, potentially due to physical features such as sandbars and mudflats that increased the availability of carcasses and provided access points for eagles.

The fate of marine-derived nutrients: tracing δ13C and δ15N through oligotrophic freshwater and linked riparian ecosystems following salmon carcass analog additions

The oligotrophic condition of salmon-bearing catchments in the Columbia River Basin is a potential limiting factor for the recovery of Pacific salmon (Oncorhynchus spp.). To address this issue, nutrient supplementation programs attempt to mitigate for reduced marine-derived nutrients (MDN). We examined the assimilation of MDN in the biota of tributaries of the Salmon River Basin, Idaho, USA, following the addition of salmon carcass analogs (SCA). We measured carbon (C) and nitrogen (N) stable isotopes from biofilm, macroinvertebrate, salmonid fish, and riparian vegetation samples and found significant 15N enrichment and substantial assimilation of SCA material in all aquatic trophic levels and in riparian vegetation. Our results suggest that SCA are incorporated primarily through indirect pathways and provide a source of MDN to multiple trophic levels in freshwater and linked riparian ecosystems.

Bioenergetic calculations evaluate changes to habitat quality for salmonid fishes in streams treated with salmon carcass analog

Nutrient supplementation in oligotrophic streams is proposed as a means of mitigating losses of marine-derived subsidies from declining or extirpated populations of anadromous fishes. One of the central predictions of nutrient addition is an increased production of fish through bottom-up increases in invertebrate abundance. Such changes in food availability may increase growth and production rates for stream fishes by increasing habitat quality. In this study we apply bioenergetic calculations to estimate changes to habitat quality based on predicted increases in net energy intake. We compared invertebrate drift abundance and estimated changes in energy availability in streams treated with salmon carcass analog versus untreated controls. Our results revealed a two- to threefold increase in invertebrate drift abundance following the addition of salmon carcass analog; however, this effect appeared to be short-term. Measures of the energetic profitability of stream habitat for salmonid fishes revealed small, yet significant, increases in net energy availability in streams that received analog additions, but only after controlling for differences in physical habitat features such as temperature and stream flow.

Biofilm nutrient limitation, metabolism, and standing crop responses to experimental application of salmon carcass analog in Idaho streams

Dramatic declines of Pacific salmon (Oncorhynchus spp.) populations have decreased delivery of marine-derived material to Pacific Northwest streams where juvenile salmon reside. Managers use artificial nutrient additions to increase juvenile salmon growth and survival and typically assume nutrient-driven increases in biofilm production are an important pathway by which nutrients become available to higher trophic levels. To evaluate how biofilms respond to additions of salmon carcass analog, a pasteurized, processed form of nutrient mitigation materials, we quantified biofilm nutrient limitation, benthic and whole-stream metabolism, and biofilm standing crops before and following experimental additions in tributaries of the Salmon River, Idaho, USA. Biofilm nutrient limitation did not change and standing crop did not increase in response to analog additions at two different levels (low, 30 g·m−2; or high, 150 g·m−2) within 1 month of addition. In contrast, whole-stream and benthic primary productivity and respiration increased in a high-analog treated segment, but did not increase in a low-analog treated segment. Together, our results suggest that metabolism may be a more appropriate tool for assessing the ecosystem effects of nutrient additions than biofilm standing crop or nutrient limitation, which are constrained by a variety of abiotic and biotic factors like hydrology and grazing.