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1. Marine aquaculture relies on coastal habitats that will be affected by climate change. This review assesses current knowledge of the threats and opportunities of climate change for aquaculture in the UK and Ireland, focusing on the most commonly farmed species, blue mussels (Mytilus edulis) and Atlantic salmon (Salmo salar). 2. There is sparse evidence to indicate that climate change is affecting aquaculture in the UK and Ireland. Impacts to date have been difficult to discern from natural environmental variability, and the pace of technological development in aquaculture overshadows effects of climatic change. However, this review of broader aquaculture literature and the likely effects of climate change suggests that over the next century, climate change has the potential to directly impact the industry. 3. Impacts are related to the industry's dependence on the marine environment for suitable biophysical conditions. For instance, changes in the frequency and strength of storms pose a risk to infrastructure, such as salmon cages. Sea-level rise will shift shoreline morphology, reducing the areal extent of some habitats that are suitable for the industry. Changes in rainfall patterns will increase the turbidity and nutrient loading of rivers, potentially triggering harmful algal blooms and negatively affecting bivalve farming. In addition, ocean acidification may disrupt the early developmental stages of shellfish. 4. Some of the most damaging but least predictable effects of climate change relate to the emergence, translocation and virulence of diseases, parasites and pathogens, although parasites and diseases in finfish aquaculture may be controlled through intervention. The spread of nuisance and non-native species is also potentially damaging. 5. Rising temperatures may create the opportunity to rear warmer water species in theUKand Ireland. Market forces, rather than technical feasibility, are likely to determine whether existing farmed species are displaced by new ones

Soy and rapeseed protein concentrates (SPC and RPC) were evaluated as fish meal substitutes in gilthead seabream Sparus aurata L. diets. The protein concentrates were used to replace 30%, 60% and 100% fish meal, and effects on feed intake, weight gain and feed gain ratio were determined in a 56‐day growth trial. Some groups were then grown beyond 56 days, until all reached an average weight of 50 g. A comparison of body composition at 50 g showed no significant differences in protein and ash content among all fish, while lipid and energy contents were different. The 100% RPC and 60% and 100% SPC replacement diets had lower body lipid and energy contents compared with those of the control diet. Feed intake and weight gains were inversely related to inclusion levels of plant proteins. Feed intake dropped to 52–72% of that of the control treatment and weight gain to 46–61%. Energy retention followed this same trend, decreasing from ERV values of 53 to 44 with an increase in dietary plant protein content. With the exception of 100% SPC substitution (PPV = 35), protein retention among treatments was similar (PPV = 37–39). These results suggest that both SPC and RPC may be promising protein sources for inclusion in seabream diets. The relative palatability of these plant proteins could be a limiting factor in their use.

Diets formulated with increasing digestible energy (10±22 DE MJ kg )1 ) contents and decreasing digestible crude protein (DCP)/DE ratios (34±15 g MJ )1 ) were fed to triplicate groups of Sparus aurata in three consecutive trials. Fish were hand-fed to apparent satiation and voluntary feed intake was found to be dependent upon dietary DE content. Daily growth was regulated both by energy and protein intake and reached its maximum at high energy levels. Growth composition showed narrow limits regarding protein gain (157±190 g kg )1 ) and a wider range regarding lipid (55± 210 g kg )1 ) deposition re¯ecting the dietary energy to protein supply. Energy utilization for growth was constant at a value of 0.50 regardless of energy intake. Eciency of protein utilization for growth varied between 0.33 and 0.60 depending on the DCP/DE ratio in the diet. The optimal protein utilization for protein deposition was found to be at 0.47. These values allow daily energy and protein requirements for growing S. aurata to be quanti®ed. This demonstrates that the optimal dietary DCP/DE supply changes with ®sh size, growth potential and daily feed intake. KEY WORDS

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Apparent digestibility of crude protein, amino acids, lipid, carbohydrate and energy was measured for a range of feed ingredients fed to gilthead seabream, Sparus aurata L. — fish meal, poultry meal, meat meal, blood meal, squid meal, extracted soyabean and wheat flour. Chromic oxide was used as a non‐absorbed reference substance and faeces were collected by stripping. Diets compounded from mixtures of these ingredients were then used to examine the possibility of predicting the digestibility of formulated diets. Apparent digestibility of crude protein ranged from 79% to 90%, lipids from 83% to 95% and energy from 72% to 88% in the different ingredients. Apparent digestibility of carbohydrates was lower and ranged from 49% to 77%. Apparent digestibility of amino acids was higher than that of crude protein and differences were found among digestibilities of individual amino acids. Tests conducted using five compound diets indicated that ingredient digestibility was additive for protein, amino acids, lipids and energy, whereas the digestibility of carbohydrates in the compound feeds was slightly lower than predicted. Diets for Sparus aurata may thus be formulated on the basis of digestibility of individual ingredients.

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