Temporal abundance patterns and growth of juvenile herring and sprat from the Thames estuary 1977–1992

Abstract

Most herring Clupea harengus and sprat Sprattus sprattus sampled from West Thurrock power station intake screens, middle Thames estuary, between 1977 and 1992 were age-0 and followed regular patterns of seasonal occurrence. Juvenile herring entered the estuary in July, peaked in abundance November to March, and then declined. Juvenile sprat first appeared in September and peaked in abundance in January. Neither species was abundant in summer samples. While in the estuary, herring and sprat increased in length an average of 4·0 and 0·33 cm respectively. Abundance of both species was significantly affected by temperature, temporal trend, shoaling behaviour and seasonal variables, and of herring by suspended solids. Interactions between environmental variates did not influence the abundance of either species. As estuarine clupeids were influenced by a complex set of events within and outside the estuary, estuarine monitoring studies alone will not be sufficient for understanding the changes in estuarine fish communities resulting from future human activity. 2000 The Fisheries Society of the British Isles

Temperature-dependent temporal variation in the size and growth of Thames estuary smelt Osmerus eperlanus

“…Temperatures were below and above average values for significant periods (Fig. 2), notably in 1983 to 1988 when average annual temperatures were at their lowest values, and in 1989, 1990 and 1992, when average annual temperatures were at their highest values as a result of drought in the southeast of England (Attrill & Power 2000). A similar temperature pattern was noted for the southern North Sea in the same period (Fig.…”

“…Despite the potential influence of variations in abundance and high variability in estuarine physico-chemical conditions (Attrill & Power 2000), inter-annual variations in the thermal opportunity for growth as represented by cumulative degree-days ≥ 5°C significantly influenced the pattern and rate of estuarine smelt growth. Estimated von Bertalanffy cohort-specific asymptotic lengths increased in warmer years, whereas growth rates (K ) declined.…”

“…Sampling began 1 h before low water and continued for a 4 h period. Nets were emptied every 30 min and all fish were identified, counted and measured for total length (mm) (Power et al 2000). When extremely large samples were obtained, a randomly selected sub-sample of the catch was measured.…”

“…Daily estuarine temperature (°C) data were obtained from Environment Agency (UK) databases (Attrill & Power 2000). Where temperature records were incomplete, linear interpolation was used to infer missing temperatures from adjacent daily means.…”

Biology of Chirocentrodon bleekerianus (Poey, 1867) (Clupeiformes: Pristigasteridae) in a continental shelf region of southern Brazil

“…The largest capture in the study area occurred in spring and the smallest in summer. Other studies (Maravelias and Reid, 1995;Power et al, 2000;Corten, 2001) stated that in certain regions, Clupeiformes were more abundant during periods of high temperatures. Nevertheless, in the internal continental shelf of Paraná State, the smallest capture values occurred in summer.…”