Historical aspects of the Firth of Forth fisheries are described, and the present state of the stocks of exploited species is reviewed. The once-substantial pelagic fisheries have declined and now constitute only a minor component of the firth fisheries. Herring fisheries were based on spring spawning herring but the herring now caught in the firth are from stocks of overwintering juveniles of autumn spawning herring. Recent conservation measures have closed many of the firth grounds to herring and sprat fishing. The main demersal species caught are cod, haddock, whiting, plaice and lemon sole. Most landings are from catches made in the middle and outer firths and the North Sea. The demersal pair trawl is now the most important gear used in directed demersal fishing. The most important shellfish fishery is that for the Norway lobster, current landings being valued at £2·4 million. Over-exploitation resulted in a decline in the stocks in the late 1970s. They are now recovering. Recent studies suggest that population characteristics of Norway lobsters are influenced by the physical environment. The firth today is one of the most intensively exploited areas in Scotland for lobster and crabs. Other exploited shellfish include squid, winkles and mussels.

Recent fishery studies in the estuary and Firth of Forth stem from the late 1970s and have largely been carried out by the Institute of Terrestrial Ecology, the Forth River Purification Board and Heriot-Watt University. This paper briefly reviews these studies, which may loosely be divided into work done at power stations, general demersal and pelagic studies of the estuarine fish populations, studies on particular species (lamprey, eelpout, whiting, cod and flatfish, especially the plaice), pollution- orientated studies (hydrocarbons in flatfish and mercury in eelpout) and more general work including ichthyoplankton surveys. Most work has been done on the ecology of flatfish, especially the plaice and it is examined in most detail.

A total of fifty species of fish have been recorded of which thirty-six occurred in the estuary and thirty-nine in the firth. Others are however known to occur. Of the twenty-eight species entrained into the intakes of local power stations, the sprat, herring, whiting and sand goby were most numerous, while other common species were sandeels, eelpout and pogge. Sand gobies, whiting, common dabs and sprats were the most numerous species taken by Agassiz trawling with herring, cod, eelpout, butterfish, pogge, flounders and plaice also commonly taken. Only herring, sprat, whiting, cod and fatherlasher were recorded using a midwater trawl and only the clupeoids occurred in all the catches. The catches of the 2 m beam trawl used in sandy bays in the firth were dominated by plaice, common dabs, sand gobies and sandeels. The ichthyoplankton surveys undertaken in 1986 have caught twenty-three species as eggs and twelve species as larvae. The majority of the eggs were those of the common dab, whiting, flounder, rock ling and sprat, while the majority of larvae were sandeels and clupeoids.

The estuary and Firth of Forth support an outstanding number and variety of wildfowl and waders at migration seasons and in midwinter. Although populations of wildfowl and waders fell from 25–35,000 and 50–65,000 respectively in the 1970s, to 10–15,000 and 30–40,000 by the mid-1980s, the Forth remains one of few British estuaries to support more than fifteen waterfowl species of national importance for conservation. The ecology and decline of diving ducks off Edinburgh and population studies of shelduck have been given particular attention by researchers. Among waders, distributions, movements and feeding have been studied in detail. The causes of the recent declines amongst waders, notably for knot (Calidris canutus) and dunlin (Calidris alpina) on the estuarine Forth, remain uncertain, but are likely to include natural factors as well as those linked to man's activities.

The seabird colonies in the Firth of Forth are spectacular. Although the total numbers of individual birds of most species are relatively small, the populations of gannet, herring and lesser black-backed gulls, sandwich, roseate, little and common terns make up more than 10% of the Scottish total. Numbers of fulmar, shag, cormorant, great black-backed gull, kittiwake, guillemot, razorbill and puffin have all increased, the rates varying from 4% per annum (kittiwake) to 20% p.a. (puffin). The numbers of cormorants stabilised soon after the species colonised the Forth in 1957. The period of rapid increase in guillemot numbers may now be over. Numbers of little terns have probably increased, but roseate and common terns have both declined and the number of sandwich terns is more-or-less stable. Herring and lesser black-backed gulls both increased dramatically up to 1972, since when breeding birds have been culled. The herring gull then decreased significantly, but the situation is less clear in the lesser black-backed gull. We set these changes in a wider context and discuss some possible reasons for the observed population trends.

Although common seals (Phoca vitulina L.) do occur in the Firth of Forth, the grey seal (Halichoerus grypus Fab.) is by far the most abundant species in the area. Some pups are born along the north shore of the outer firth but the vast majority are born on the Isle of May. This colony has increased in size from less than twenty-five pups in 1975 to more than 900 in 1986. Studies using conventional and radio tags indicate that many of the seals at the Isle of May originally came from the colony at the Farne Islands, off the Northumberland coast. Information from the Fame Islands population is used to predict future changes at the Isle of May. If current trends continue, more than 2000 pups could be born each year by the end of the century. However, it seems unlikely that this will occur. Management methods for controlling habitat damage are discussed.

The Forth is of great importance for nature conservation. More than half of the coastline of the estuary and the Firth of Forth is assessed to be sufficiently important for designation as Sites of Special Scientific Interest (SSSIs). The basis of the selection of these sites is discussed. The SSSIs are then described, including those which are managed as nature reserves. Wider aspects of conservation in the Forth are referred to. The main threats to wildlife sites and species are indicated, together with possible solutions, and opportunities for conservation.