Search

Mature thorny (Amblyraja radiata), winter (Leucoraja ocellata), and smooth (Malacoraja senta) skates have declined to very low abundance in the southern Gulf of St. Lawrence (SGSL) and on the eastern Scotian Shelf (ESS). We used stage-structured state-space models to examine decadal patterns in mortality rates in these skates. Mortality at early life stages (embryos in egg cases, hatchlings, and (or) small juveniles) appeared to decrease between the 1970s and the 2000s. In contrast, estimated mortality rates increased for larger individuals over this period. Although potentially confounded in models with effects of any changes in juvenile growth, the estimated increases in mortality could not instead be attributed solely to changes in growth. Increases in the mortality of large individuals appeared to reflect increases in natural mortality, possibly due to predation by grey seals. Increases in natural mortality were not evident for skates on the neighbouring western Scotian Shelf, where grey seal abundance has remained lower. Even in the absence of fishing, recovery of skates is unlikely under current ecosystem conditions in the SGSL and on the ESS. Les raies epineuses (Amblyraja radiata), tachetees (Leucoraja ocellata) et a queue de velours (Malacoraja senta) matures sont devenues tres peu abondantes dans le sud du golfe du Saint-Laurent (SGSL) et l'est du plateau neo-ecossais (ESS). Nous avons utilise des modeles d'espaces d'etats structures selon les etapes du cycle de vie afin d'examiner les patrons decennaux des taux de mortalite chez ces raies. La mortalite durant les premieres etapes du cycle de vie (embryons dans les capsules d'oeufs, alevins vesicules et petits juveniles) semble diminuer entre les annees 1970 et les annees 2000. En revanche, pour les individus plus grands, les taux de mortalite estimes ont augmente au cours de cette periode. Si, dans les modeles, les augmentations estimees de la mortalite peuvent potentiellement se confondre avec les effets de changements de la croissance des juveniles, elles ne peuvent toutefois etre entierement attribuees a de tels changements. Les augmentations de la mortalite des grands individus semblent refleter des augmentations de la mortalite naturelle possiblement dues a la predation par les phoques gris. Aucune augmentation claire de la mortalite naturelle n'a ete notee pour les raies de la partie ouest du plateau neo-ecossais, ou l'abondance des phoques gris est demeuree plus faible. Meme en l'absence de peche, un retablissement des raies est peu probable dans les conditions ecosystemiques actuelles dans le SGSL et le ESS. [Traduit par la Redaction], Introduction Elasmobranch fishes, especially the larger species, are considered to be among the most vulnerable fishes to exploitation because of their life-history characteristics, in particular late maturation, large adult size, [...]

A method has been established for the identification of proanthocyanidins and quantification of individual monoproanthocyanidins using liquid chromatography/electrospray ionization-mass spectrometric detection (LC/ESI-MSD) for raw grape products. The separated monoproanthocyanidins and oligoproanthocyanidins were individually analyzed and identified by their molecular ion peaks using LC/MS. Using HPLC/ESI-MSD, the proanthocyanidin monomers, (+)-catechin (C), (-)-epicatechin (EC), (-)-catechin gallate (CG), and (-)-epicatechin gallate (ECG) in grape products were successfully quantified by LC/MS/MS detection of protonated molecular ions and characteristic fragment ions for each component under the optimized low collision energy level of 20%. For the investigated concentration ranges of C (21.88-11 200 ng/mL), EC (21.10-10 800 ng/mL), CG (36.72-18 800 ng/mL), and ECG (39.84-20 400 ng/mL), good linearities ([r.sup.2] > 0.99) for standard curves were obtained. Validation of this method showed an accuracy that was well below 15% and precision (RSD) within 8% for the four compounds. The method proposed here is simple, sensitive, and allows a direct sample preparation procedure. This is the first method that enables the determination of individual monoproanthocyanidins in grape products without any solid-phase extraction.