Previous North Sea food web studies are reviewed. These studies used estimates of primary production and fish energy requirements, then manipulated the energy flow pathway between the two to balance the budget. The resulting pathways largely ignored actual fish diets and consumption rates. In the present paper, North Sea biomass flow food webs are constructed for each quarter of the year from published estimates of fish abundance, diet and daily food consumption, and using long-term Continuous Plankton Recorder and North Sea benthos survey data. Estimates of daily production of each component of the web are derived from specific daily growth and gross growth efficiency measurements. The flow of biomass from secondary production to fish is sufficient to supply the food requirements of planktivorous pelagic fish and benthivorous demersal fish. Piscivorous pelagic fish obtain much of their food requirements from outside the North Sea. The food requirements of piscivorous demersal fish also do not appear to be adequately supplied from within the North Sea, but, in this case, immigration is not thought to provide the shortfall. The high predation pressure on demersal piscivores may explain why this group appears to be especially vulnerable to fishing. The supply of biomass from primary production to secondary producers appears to be sufficient without the need to postulate import into the North Sea. Indeed, the supply to the benthos is such that a detritivore trophic level can be inserted between organic settlement and production of macrobenthos

A computer model for epilithic algae and grazer biomass in streams is modified to better predict the effects of temperature and is calibrated for diatoms and mayflies. Mayflies are predicted to maintain low diatom biomass provided that (1) temperatures remain within their preferred range (10-20ЊC); and (2) mayfly populations are not adversely affected by floods. Algal blooms are predicted to occur in mayfly-dominated streams above 20ЊC-temperatures common in pasture streams over summer. We hypothesize that mobile bed streams are susceptible to blooms during summer low flows following floods because (1) they usually lack temperature tolerant snail grazers; and (2) mayfly recovery lags behind algal regrowth, and there is a short period when algae escape from ''top-down'' grazer control.

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The dispersal and transport of larval New Zealand abalone Haliotis iris was simulated using coupled two-dimensional hydrodynamic and Lagrangian particle-trajectory models. The aim was to estimate pelagic larval dispersal potential along the open coast, as a starting point from which basic management questions can be made for this recreationally and commercially important species. Larval dispersal was simulated from representative spawning sites under a range of representative hydrodynamic conditions, including wave-induced circulation cells. Larval presence over near-shore reef habitat declined as the energy of the flow field and corresponding larval dispersal and transport increased. Thus, spawning during high-energy conditions will promote dispersal and transport but reduce successful recruitment on near-shore reefs. This indicates that seeding of the adjacent coast is likely to be sporadic, with existing populations necessarily being somewhat self-recruiting. Results suggest that an ideal management system would ensure that adult populations were maintained at intervals of 10–30 km along the coast to maintain larval supply to areas in between. Dispersal characteristics were specific to the release site, and the simulations suggest that marine reserves can be positioned to accordingly achieve desired functions: for example, optimal choices can be made for seeding areas, recruitment or self-maintaining areas.