The role of prey composition for the condition of grey gurnard (Eutrigla gurnardus)

Abstract

During a fisheries research cruise on the Dogger Bank in the central North Sea, we studied the role of diet for the condition of grey gurnard (Eutrigla gurnardus). Seventeen stations across the Dogger Bank were sampled with the GOV otter trawl in April⁄May 2006. Each fish sampled was categorised according to three feeding types: a predator specialised on fish, on invertebrates or having a mixed diet, depending on the percentage of fish and⁄or invertebrates in the stomach. These predator-prey categories were compared by means of three condition indices: FultonÕs condition factor, a hepatosomatic index (HSI) and a gonadosomatic index (GSI). FultonÕs condition factor provided evidence that a specialisation on fish prey increases the condition of grey gurnards in terms of the length-specific individual weight. In contrast, the HSI scored highest for predators feeding on a mixed diet. The GSI showed a tendency to be highest with a diet dominated by invertebrate prey, but differences between the three predatorprey categories were not significant. Based on the topography of the Dogger Bank, stations were allocated in shallow and deep regions. At shallow stations, the brown shrimp Crangon allmani and sandeels, combining basically the taxa Ammodytidae, Ammodytes juv. and Ammodytes marinus, were typically observed in stomach contents of gurnards whereas the amphipod Hyperia galba was predominantly found in gurnards sampled in deep regions.

Seasonal and spatial variations in prey utilization and condition of a piscivorous flatfish Paralichthys olivaceus

“…7) might also reflect the difference in prey availability, although no evidence for this was observed; SCI during this period was lower in the northern area. The importance of prey utilization for the condition of predatory fishes has also been suggested for other demersal fishes such as Greenland halibut Reinhardtius hippoglossoides (Román et al 2007), Atlantic cod Gadus morhua (Pardoe et al 2008), bighand thornyhead Sebastolobus macrochir (Hattori et al 2009), and grey gurnard Eutrigla gurnardus (Weinert et al 2010).…”

Occurrence and distribution of anisakid nematodes in Grey gurnard (Eutrigla gurnardus L.) from the North Sea

“…Additionally, the differences in H. aduncum infection parameters between the localities may reflect the ecological characteristics of each. For example, differences between gurnard localities in the North Sea regarding the occurrence or abundance of preferred prey items (Weinert, Floeter, Kröncke, & Sell, 2010), which may also act as intermediate or transport hosts for H. aduncum, could significantly influence the infection level of this nematode species in Grey gurnard as well. From the present data, the differences in infection level between A. simplex and H. aduncum in both localities are not readily explained.…”

Occurrence and distribution of parasites in relation to food components of grey gurnard, Eutrigla gurnardus (L.) (Teleostei: Scorpaeniformes), off the Shetland Islands

“…In the work by Weinert et al (2010), the highest HSI values were recorded for specimens with a mixed diet. All parasites of grey gurnard from the area of the Shetland Islands have complex life cycles and are passed passively through the food chain into the fish, which are the intermediate (paratenic) or definitive hosts.…”

“…The ratio of fish to invertebrates in gurnard stomachs can largely vary from year to year, and Kotterba (2008) reported that the average contribution of fish to the diet in the 25-30 cm length class was 72.8% and 20.2% in 1991 and 2007, respectively. Studies conducted by Weinert et al (2010) in the vicinity of the Dogger Bank in the central North Sea revealed that the amphipod Hyperia alba was the most abundant species found in gurnard stomachs, followed by Crangon allmani, and that the dominant vertebrates included the sandeel family (Ammodytidae) together with the species Ammodytes marinus. In the present study, the euphausiid Euphausia krohnii was the most abundant species, while poor cod Trisopterus minutus (Gadidae) dominated the vertebrates.…”