Trophic structure within the Bristol Channel: seasonality and stability in Bridgwater Bay

Abstract

A general description of the trophic inter-relationships and the food web within Bridgwater Bay, Somerset, England, is presented. This Bay is a lower estuarine site within the Bristol Channel. Particular attention is given to the use of the area by fish and larger crustaceans which are the dominant animal groups. Using data collected over a ten-year period of monthly sampling, the relative average biomass of all fish and larger crustaceans found within the Bay is calculated for each month of the year. These averages are used to produce food webs which also show species relative abundance for each calendar month.It is shown that the trophic structure follows a seasonal cycle due to migration. The application of the concept of stability within such a dynamic system is discussed. The role of compartmentalization of the ecosystem into a number of loosely connected groups as an aid to overall stability is discussed. While there is no evidence that contemporaneous compartments exist, it is argued that inter-specific interactions are temporally limited because of the different periods of annual residence of the species. It is suggested that the stability and resilience to interference shown by these estuarine systems is enhanced by temporal partitions.

Fluctuations of brown shrimp Crangon crangon abundance in the western Dutch Wadden Sea

“…Finally, Gadiform abundance in autumn was included in the spring model and negatively related to Crangon crangon abundance. Despite including whiting Merlangius merlangus, a very abundant and important predator of brown shrimp (Henderson & Holmes 1989, Henderson et al 1992, Hamerlynck & Hostens 1993, Singh-Renton & Bromley 1999), Gadiforms did not show a significant cross-correlation with the Dutch Wadden Sea shrimp abundances, contradicting the observations in the German area (Siegel et al 2005) and in the Bristol Channel (Henderson et al 2006). However, the abundance of Gadiforms was correlated with the abundance of other predators especially Scorpaeniforms.…”

“…d -1 ) of brown shrimp (CRANG) and potential predators grouped at Order level were then extracted from the database and mean daily abundances were determined for each season (see below). The potential predators included Clupeiforms (CLUP), Gadiforms (GAD), Perciforms (PERC), Scorpaeniforms (SCORP), Pleuronectiforms (FLAT) and Decapods (CRAB) (Tiews 1970, De Vlas 1979, Pihl 1985, Henderson & Holmes 1989, Henderson et al 1992, Hamerlynck & Hostens 1993, Berghahn 1996, Cattrijsse et al 1997). …”

“…Populations show a clear genetic structure, with distinct NE Atlantic and Mediterranean populations (Luttikhuizen et al 2008). Due to its high abundance, C. crangon forms a key component of the trophic web: it is an important food source for several predators including fish, crustaceans and shorebirds (Pihl 1985, Henderson et al 1992, del Norte-Campos & Temming 1994, Walter & Becker 1997) and, in turn, it preys heavily upon numerous benthic species such as bivalve spat and juvenile flatfish (Pihl & Rosenberg 1984, van der Veer et al 1991, 1998, Ansell & Gibson 1993, Oh et al 2001, Amara & Paul 2003. In addition to its important ecological role, brown shrimp is a valuable fisheries resource, especially around the North Sea (Polet 2002, ICES 2008.…”

Seasonal, annual and regional variations in ichthyofaunal composition in the inner Severn Estuary and inner Bristol Channel

“…Since estuaries are highly productive ecosystems (Schelske & Odum, 1970) and thereby facilitate the rapid growth of juvenile fish, it is relevant that the inshore shallows of the Oldbury region contain high densities of small crustaceans, which are an important food source for juvenile fish in the region (Moore & Moore, 1976;Moore et al, 1979;Henderson et al, 1992). The important role played by the shallows of the Severn Estuary as a nursery ground for certain marine species parallels the situation recorded in temperate estuaries elsewhere in the Northern Hemisphere and also in the Southern Hemisphere (e.g.…”

Multispecies impingement in a tropical power plant, Straits of Malacca

“…Several studies by Henderson and co-workers (e.g. 385 Henderson, 1989;Henderson et al, 1992) have shown how potentially useful power plant catches can be utilized to advance scientific knowledge on carrying capacity, niche occupation and trophic structure, and in the process, to give good advice pertaining to power plant siting and operations.…”