Converging results in different scientific fields (behavioural ecology, fisheriesbiology, acoustic tagging, fisheries acoustics, behavioural modelling) suggest theexistence of “micro-groups” inside fish schools. These would comprise a few (5–10) fishmaintaining contact during a period long enough to allow individuals to recognise eachother. It is hypothesised that they would prefer to share the space with familiar ratherthan anonymous conspecifics. To evaluate whether acoustic methods could be used torecognise “micro-structures” inside fish schools and help test the “micro-group” hypothesiswe analysed acoustic data from anchovy schools off Peru, and gadoids in the North Sea.Data collection used a multibeam sonar (Reson SeaBat 6012). In the Peruvian case study,the sonar was mounted set horizontally on a drifting research vessel and the internalstructure of the schools of anchovies was analysed, although individual fish could not bediscriminated. In the North Sea case study, the sonar was orientated vertically above ademersal trawl to allow observation of individual fish entering the trawl. Geostatisticalanalyses were used to evaluate the existence of small spatial structures in anchovyschools. In these schools, “micro-structures” with a scale as small as 0.5 m were observedacoustically. For the gadoids nearest neighbour distance (NDD) measurements were carriedout, suggesting that the fish aggregated in small groups (2 to 25 individuals, with anaverage of 3.7 fish per group) in the trawl catches. The perspectives and limitations ofthese results are discussed.

The curve used until recently by the International Commission for the Conservation ofAtlantic Tunas (ICCAT) to represent the growth of western Atlantic bluefin tuna,Thunnus thynnus, was estimated using tagging information and modalsizes that corresponded primarily to very young fish (ages 1–3, primarily). The estimatedmaximum average size from this curve is very large (382 cm), which could be a result ofthe scarcity of large bluefin in the data used. Recently, scientists have developedtechniques for reading ages from bluefin ear bones (otoliths); the accuracy of the agereadings has been validated with bomb radiocarbon dating. These age readings are primarilyfor large bluefin (ages 5 and older), and indicate slower growth and older ages than waspreviously assumed. However, an analysis of these data resulted in growth curves thatpredicted very small mean sizes for the youngest age group, which could be a result of thelack of small fish in the data used. In this study, we combine the otolith-based agereadings with the size frequency distributions of small (ages 1–3) bluefin caught by purseseiners in the 1970s where the age groups are distinctly statistically as well as visibleto the eye. We analyzed the two datasets jointly using a maximum likelihood approach andassumed that variability in length-at-age increases with age. The resulting growth curvepredicts sizes at young and old ages that are very consistent with observed data such asthe maximum sizes observed in the catch and the modal sizes for very young bluefin. Theresulting curve is also very similar to the curve used by ICCAT for eastern Atlantic andMediterranean bluefin.

This work focuses on investigating the potential of calcein and manganese as growthmarkers of the common cockle (Cerastoderma edule) in the bay of Somme(France). Recapture of shells, previously marked using a chemical marking and then bred innatural conditions, was performed in order to determine the shell growth patterns. Calceinmarking has shown a fluorescent increment in shells after only 30 min immersion time at150 mg L-1, but also for shells immersed 3 h at 50 mg L-1. Likewise,manganese shell marking was revealed under cathodoluminescence for shells immersed 1 h at120 mg L-1 as well as for shells which spent 4 h at 90 mg L-1. Anumerical analysis performed on each marked cockles has revealed 23 micro-incrementsbetween the mark and the ventral edge of the valves, corresponding to the 23 tides thatoccurred during the 12 days at liberty post marking. The periodicity of incrementformation is thus validated for a tidal frequency. The growth rates of C.edule, ranged from 11.67 to 19.94 μm d-1, decreasedsignificantly with increasing shell length. This preliminary study gives a clue to theunderstanding of cockle growth and could be used in shellfish production for cockle agemonitoring, but also for chemical analysis to learn more about biomineralization processof this species.

Simulation of fisheries systems is a widely used approach that integrates monitoring and assessment tools. We applied the ALADYM (age-length based dynamic model) simulation model to three different studies aimed at investigating correlations between pressure and population metrics, exploring the viability of different mortality levels in long-term scenarios and predicting the effects of combined management measures. Uncertainty was incorporated into the simulations following the Monte Carlo paradigm. Three stocks were used for these exercises: red mullet in the central-southern Tyrrhenian Sea and European hake in both the Bay of Biscay and the Aegean Sea. The analysis of the relationships between total mortality and indicators highlighted significant pairwise negative correlations for red mullet. These signals of decline were supported by the spawning potential ratio indicator (mean exploited to mean unexploited spawning-stock biomass ESSB/USSB), which was low compared to target levels. It only remained within safe bounds (>0.2; probability: 0.90–0.95) at total mortality levels lower than 1.6. The simulation results for European hake in the Bay of Biscay showed that a sustainable exploitation rate might range from 0.87 to 1.04. The benefits of combined management measures were demonstrated for European hake in the Aegean Sea, and with a further dataset on the Eastern cod stock in the Baltic Sea.

Uncertainty about reporting rates of tags returned by fishermen has often prevented tagging data from being used in stock assessments. In this study we conduct a meta-analysis to estimate tag reporting rates of commercial tuna fleets by comparing their tag return data with those of the USA longline pelagic observer program. The longline fleets of Venezuela and the USA are estimated to report about 0.8% of tags caught, compared with less than 0.1% for Canadian, Spanish and Japanese longline fleets. For some fleets with sparse return data or for those that do not overlap often with the observer fleet, reporting rate estimates are sensitive to changes in the spatio-temporal resolution over which comparisons are made. Regardless of these sensitivities, the estimated reporting rates are low and there are likely to be large differences in reporting rate between different combinations of flag and gear.

Catch-at-size data of the eastern Atlantic skipjack were used to estimate changes in total mortality from 1969 to 2007. We used a transitional model of mean length that generalized the Beverton-Holt mortality estimator to allow change in mortality rate under nonequilibrium conditions. Then, from homogeneous periods of time, length-converted catch curves were used to access qualitative changes in selectivity patterns for two surface fisheries (the baitboat fishery operating from Dakar, Senegal, and the European and associated purse seine fisheries). To explore the impact of catch on the mortality rate, a Bayesian change-point analysis was conducted on the catch time series to detect concomitant variation between mortality rates and catch. Finally, potential causes of these changes are discussed in relation to the implementation of new fishing technology, such fish aggregating devices (FAD). The general pattern depicted by total mortality is in agreement with previous knowledge on this fishery: a state of complete or practically complete exploitation during the nineties followed by the decrease in nominal purse seine fishing effort in the last decade, combined with the effect of a seasonal moratorium on FAD fishing operations. There was no evidence of a change in selectivity between the two contrasted periods of time considered: 1969-1979 and 1986-1999; the second period being characterized by the introduction of new technology onboard vessels. In contrast, the covariation over time between total catch and mortality rate three years later highlights the effect of the fishing pressure on the stock of eastern Atlantic skipjack.

We sampled 27 month-old mussel populations grown on collector ropes in Cascapédia Bay,Quebec, to test whether density-dependent growth was present concomitantly toself-thinning, a process which was previously shown to occur in this system and thought tobe driven by spatial constraints. Biomass-density curves of raw samples were curvilinear,suggesting density-dependent growth. However, at least two cohorts were present.Fractionating the samples on the basis of age yielded a linear relationship for the main,2 year-old cohort. This implies density-independent growth and rules out food regulationin these populations. Therefore, our results are consistent with inferences drawnpreviously from the values of the self-thinning exponent, that is, space-regulatedself-thinning. Our results suggest that curvilinearity of the raw biomass-density curvesresulted from a bias caused by including the 1 year-old cohort and spat of the year in theanalysis. This conclusion is supported by a model showing that samples with mixed cohortscan yield linear, concave or convex biomass-density curves without density-dependentgrowth. The shape of the curves depends on the scaling relationships between cohortabundances. It appears that the shape of biomass-density curves may be a usefulcomplementary criterion – in addition to the value of self-thinning exponents – for theidentification of food or space as factors regulating cultured populations.

The objective of this study was to identify a possible effect of food on the accelerationof decontamination in blue mussels, Mytilus edulis, containing diarrhetictoxins belonging to the okadaic acid (OA) structural group. An experimental protocol wasdesigned to describe and compare the decontamination kinetics and detoxification rates ofnaturally OA-contaminated mussels that had either received or not received food for threeweeks. The protocol was applied in two trials (in June 2006 and June 2007, called Ker06and Ker07), conducted one year apart on samples of mussels collected in the same area, atthe same season. Okadaic acid (OA), the main lipophilic toxin produced by the toxic algaDinophysis acuminata, was analysed over the course of thedecontamination, in hydrolysed (total OA) and non hydrolysed (free OA) digestive glandextracts, in order to estimate acyl-esters (7-O-acyl-ester derivatives ofOA) concentrations. OA analyses were also made for toxin presence in biodeposits and inthe aqueous phase. Bivalve physiological status was evaluated by biomass measurements (dryweight of flesh) and two biochemical compounds (total lipid and glycogen concentrations).Measured physiological parameters showed that mussels did not suffer under experimentalconditions. Both trials showed that the food accelerated the elimination of free and totalOA. This effect cannot be attributed to a dilution of the toxin in the tissue, as resultsexpressed in toxin burden led to the same conclusion. The kinetic models ofdecontamination differed between the two experiments: the model was linear for Ker06,provided that the values corresponding to the first two days were discarded, whereas datafitted a decreasing exponential curve better in Ker07. Detoxification rates increased asthe food supply increased. After three weeks of experimentation, the detoxification ratesfor total OA in Ker06 and Ker07 were 52 and 61%, respectively, in unfed mussels and 90 and89% in fed mussels (with the highest level in Ker07). Comparisons between the free OA andesters showed that detoxification rate was higher for free OA than for esters, whateverthe level of food supply. The results of this study suggest that food increase probablyaccelerates elimination of OA and OA-esters but the latter are eliminated at a lowerspeed.

Fin spine ageing is the most common technique used to estimate age and growth parameters of large pelagic billfishes from the families Istiophoridae and Xiphiidae. The most suitable methods for processing and interpreting these calcified structures for age estimation have not been clearly defined. Methodological differences between unvalidated ageing studies are of particular concern for highly migratory species because multiple researchers in different regions of the world may conduct age estimates on the same species or stock. This review provides a critical overview of the methods used in previous fin spine ageing studies on billfishes and provides recommendations towards the development of a standardized protocol for estimating the age of striped marlin, Kajikia audax and white marlin, Kajikia albida. Three on-going fin spine ageing studies from Australia, Hawaii, and Florida are used to illustrate some of the considerations and difficulties encountered when developing an ageing protocol for highly migratory fish species. Particular areas of concern that may influence age and growth estimates included differences in fin spine selection, sectioning methods, criteria for identifying and measuring annuli, distinguishing false annuli, validation procedures, identification of the first annulus, and methods used to replace annuli lost due to vascularization of the fin spine core.

Bycatch of several groups of species and their characteristics are presented for the period 2003 to 2007 for the European purse seine tuna fishery operating in the Atlantic Ocean. Data were collected through French and Spanish observer programmes and represented a total of 27 trips corresponding to 2.9% coverage. Bycatch is defined as non-targeted species and small or damaged target species. Bycatch species composition, main species length, sex ratio and the fate of the most common species are presented first. Stratified ratios relative to landings of major commercial tunas were then used to estimate the total bycatch; these ratios were considered the most appropriate variable for extrapolation. Stratification was based on the fishing mode (free school vs. floating object), season (quarters) and spatial areas. The annual average bycatch was estimated at about 6400 t, corresponding to a mean annual value of 80.8 t per 1000 t of tuna landed or 7.5% of the total catch. Tunas represent 83% (67.2 t/1000 t) of the total bycatch, followed by other bony fishes (10%, 7.8 t/1000 t), billfishes (5%, 4.0 t/1000 t), sharks (1%, 0.9 t/1000 t) and rays (1%, 0.9 t/1000 t). Based on estimates of the annual bycatch, 16% was kept on board and sold in local markets.

We analyzed stable isotopes of carbon and nitrogen to investigate the trophic structureof the subtidal food web around the Mingan Islands, northern Gulf of St. Lawrence, easternCanada. All benthic consumers were enriched in 13C (mean δ13C of–17.1‰) compared to particulate organic matter (POM: –23.3‰). Nitrogen stable isotoperatios ranged from 6‰ to 14‰ and the organisms studied fell into three distinct trophicgroups, primary producers, primary consumers (herbivores), and predators. The sea starCrossaster papposus and the sculpin Myoxocephalusscorpius, known to be top level predators, had slightly higher δ15Nthan other predators. Although the average isotope signature of the sea starSolaster endeca placed it among regular predators, the δ15Nincreased with sea star size and large individuals could be considered as top predators.The relatively small number of organisms located at intermediate trophic levels suggests alow level of omnivory in the Mingan Islands’ system, which contrasts with previouslydescribed benthic systems that exhibit a continuum between herbivores and predators. Lowomnivory, in addition to low diversity, suggests that this ecosystem may be relativelyunstable if exposed to natural and/or anthropogenic disturbances such as exploitation andclimate change.

Gametogenic cycle, gross biochemical composition, condition indices and soft tissuecaloric value of the brown mussel Perna perna were investigated in thecoastal waters of the Gulf of Aden over ten months, to delineate ecophysiologicalperformance of the bivalve. The timing of reproductive activity and seasonal variations ofphysiological features appear to depend on interaction of environmental (exogenous) andinternal (endogenous) factors. Two major spawning events occurred during seasonal monsoonsi.e. in late summer (SW monsoon, August-September) and early spring (NW monsoon,February-March), although these differed considerably in relative intensity and the extentof the resulting changes in physiology and body weight. The summer breeding, which wascorrelated with low water temperature and abundant food, exerted little effect onbiochemical constituents, indicating protracted and portioned spawning. Reserve stores(lipids, carbohydrates and proteins) accumulated gradually in the cooler inter-monsoonperiod of gametogenic quiescence, to provide energy for periods of natural nutritionalstress when water temperature increased and primary production diminished. The secondspawning in spring was accompanied by a substantial decrease in lipids, carbohydrates andcondition indices of the mussels probably due to the release of nutrient-rich gametes inadaptive response to lower food availability in the environment. High reproductive effortpresumably induced increased mortality of females, which were strongly outnumbered bymales at a ratio of 1.8:1.0. Caloric value of this mussel falls within a range typical formussel species in other subtropical areas, highlighting the importance of Pernaperna as a local food resource and its potential suitability foraquaculture.

Incidental catch or bycatch represents a significant threat for the conservation of seabird populations. The western Mediterranean is an important fishing area where the Spanish pelagic and semi-pelagic longline fleet targeting swordfish (Xiphias gladius), bluefin tuna (Thunnus thynnus) and albacore (Thunnus alalunga) operates. Bycatch of these fisheries includes several seabird species. Given the importance of conservation of the bycatch species (marine mammals, turtles, sharks and seabirds), an on-board observer program was implemented by the Spanish Oceanographic Institute (IEO); this included collecting data on effort and catch, as well as weight and number of individuals of the main bycatch species. The aim of the present study is to report data on seabird bycatch collected by the on-board observer program of the IEO in the Western Mediterranean. Data on seabird bycatch were collected for the period 2000-2008, throughout the year. Six longline gears targeting large pelagic fish were identified operating in the area of study, but only three had an effect on seabird species. Differences in catch per unit effort (CPUE, birds per 1000 hooks) for each gear, as well as their effect on particular seabird species, are reported in this study. A total of 4 786 466 hooks were monitored, which yielded 182 seabirds belonging to 7 different species. The average CPUE for the studied period was 0.038 birds per 1000 hooks. Cory’s shearwater (Calonectris diomedea) and yellow-legged gull (Larus michahellis) were the species the most highly represented in the catch. In contrast, Balearic shearwater (Puffinus mauretanicus) was only present in the longline fishery targeting albacore (CPUE = 0.005 birds per 1000 hooks). Our results suggest that Cory’s shearwater is the species the most affected by the longline fishery in the Western Mediterranean, probably due to its biological characteristics, and corroborate the well-established downward trend in its population.

An ecological risk assessment (ERA; also known as productivity and susceptibility analysis, PSA) was conducted on eleven species of pelagic elasmobranchs (10 sharks and 1 ray) to assess their vulnerability to pelagic longline fisheries in the Atlantic Ocean. This was a level-3 quantitative assessment consisting of a risk analysis to evaluate the biological productivity of these species and a susceptibility analysis to assess their propensity to capture and mortality in pelagic longline fisheries. The risk analysis estimated productivity (intrinsic rate of increase, r) using a stochastic Leslie matrix approach that incorporated uncertainty in age at maturity, lifespan, age-specific natural mortality and fecundity. Susceptibility to the fishery was calculated as the product of four components, which were also calculated quantitatively: availability of the species to the fleet, encounterability of the gear given the species vertical distribution, gear selectivity and post-capture mortality. Information from observer programs by several ICCAT nations was used to derive fleet-specific susceptibility values. Results indicated that most species of pelagic sharks have low productivities and varying levels of susceptibility to pelagic longline gear. A number of species were grouped near the high-risk area of the productivity-susceptibility plot, particularly the silky (Carcharhinus falciformis), shortfin mako (Isurus oxyrinchus), and bigeye thresher (Alopias superciliosus) sharks. Other species, such as the oceanic whitetip (Carcharhinus longimanus) and longfin mako (Isurus paucus) sharks, are also highly vulnerable. The blue shark (Prionace glauca) has intermediate vulnerability, whereas the smooth hammerhead (Sphyrna zygaena), scalloped hammerhead (Sphyrna lewini), and porbeagle (Lamna nasus) sharks are less vulnerable, and the pelagic stingray (Pteroplatytrygon violacea) and common thresher (Alopias vulpinus) sharks have the lowest vulnerabilities. As a group, pelagic sharks are particularly vulnerable to pelagic longline fisheries mostly as a result of their limited productivity.


The broad-scale effects of salmon farming on benthic and epibenthic macrofaunalcommunities of four Scottish sea lochs (Kishorn, Duich, Hourn and Nevis) with differentaquaculture loadings were investigated based on the first benthic surveys to be undertakenin these lochs. Significant variation in the benthic communities was identified betweenlochs, mainly related to differences in the abundance of echinoderms and polychaetes (thedominant components of the benthic communities). Variance partitioning using partialredundancy analysis suggested that approximately 9.6% of this variation could be relatedto aquaculture activity in the lochs (as expressed through “production” and previouslymodelled “impact” levels), as compared to 20.6% attributable to measured environmentalfactors. Epibenthic communities were dominated by echinoderms and arthropods and there wasno significant between-loch variation in epibenthic community composition. No significantdifferences were apparent in the benthic or epibenthic community assemblages betweensamples taken within 2000 m of a fish farm and those taken beyond this distance. Ingeneral, our results support previous studies suggesting a spatially limited impact ofsalmon culture installations on the benthos, although impacts on the aquatic food web on awide spatial scale cannot be ruled out and the link between benthic community variationand aquaculture variables identified through variance partitioning requires furtherinvestigation.

Fishery independent indices of spawning biomass of Atlantic bluefin tuna in western North Atlantic Ocean are presented which utilize National Marine Fisheries Service ichthyoplankton survey data collected from 1977 through 2007 in the Gulf of Mexico. Indices were developed using similarly standardized data from which previous indices were developed (i.e. abundance of larvae with a first daily otolith increment formed per 100 m2 of water sampled with bongo gear). Indices were also developed for the first time from standardized data collected with neuston gear [i.e. abundance of 5-mm larvae (i.e. seven-day-old larvae) per 10 minute tow]. Indices of larval abundance were developed using delta-lognormal models, including following covariates: time of day, time of month, area sampled and year. Due to the large frequency of zero catches during ichthyoplankton surveys, a zero-inflated delta-lognormal approach was also used to develop indices. Finally, a multivariate delta-lognormal approach was employed to develop indices of annual abundance based on both bongo and neuston catches. The results of these approaches were compared with one another and with other indices of larval abundance previously developed for the Gulf of Mexico. Residual analyses indicated that abundance indices of Atlantic bluefin tuna larvae were more appropriately developed from bongo-collected data through the zero-inflated delta-lognormal approach than other data sets and modeling approaches. Also, when modeling bongo-collected data with the zero-inflated delta-lognormal approach, the index values increased, indicating some correction for zero-inflation, and their variability decreased as compared to indices developed with the delta-lognormal approach.

Initiatives for the sustainable development of aquaculture have so far focused on theproduction of codes of conduct, of best management practices, of standards etc., most ofwhich have been developed by international organisations, the industrial sector and nongovernmental organisations. They were, to a large extent, produced using a “topdown” process and inspired by models from intensive industrial shrimp and sea fish farming(mainly salmon). However, most of global aquaculture production comes from small- andmedium-sized farms, essentially in Asia which contributes 92% of the total worldaquaculture production volume. The objective of this article is to define the contours ofsystemic typologies that are able to express the sustainability conditions of aquaculturesystems. The proposed approach builds on surveys of aquaculture systems which differ interms of their biogeographical nature (temperate/tropical and north/south countries) ortheir farming techniques and their governance systems. This work is a prerequisite to anyattempt at an individualised and comparative evaluation of specific aquaculture systemsfrom either global or territorial viewpoints. In order to go beyond the cleavage of atypology based on the differentiation between developed and developing countries, threetypologies were produced. These typologies allow for discriminatory variables to beidentified such as for example the marketing methods or the pace of innovation: astructural typology, a functional typology and a systemic typology. Finally, therepresentations of aquaculture activity and of its sustainability that producers have ofthe 4 different types that emerge from the systemic typology were recorded andanalyzed.

Distribution and relative abundance of blue sharks (Prionace glauca) in the southwestern Atlantic Ocean was modeled based on catch-per-unit-effort (CPUE) per 1000 hooks and length frequencies of blue sharks caught by the Brazilian pelagic tuna longline fleet. As a measure of relative abundance, CPUE of blue sharks caught in 58 238 fishing sets by the Brazilian pelagic tuna longline fleet (national and chartered), from 1978 to 2009, was standardized by a Generalized Linear Model (GLM) using three different approaches: i) a negative binomial error structure (log link); ii) the traditional delta lognormal model; and iii) the Tweedie distribution, recently proposed to adjust models with a high proportion of zeros. A cluster analysis using the K-means method was used to identify target species and incorporate it as a factor into the GLM. Cluster analysis grouped the data into six different fishing clusters according to the percentage of target species. Target factor (cluster) was the most important factor explaining the variance in all three CPUE models. The Tweedie model showed a relatively better fit compared to the other models. Blue shark nominal and standardized CPUE showed a relatively stable trend from 1978 to 1995. From 1995 onwards, however, there was an increasing trend in the standardized CPUE, up to a maximum value in 2008. In general, nominal CPUE and standardized CPUE tracked well up until 2000, after which standardized CPUE’s values were at a noticeably lower level than nominal CPUE. Length frequency data were analyzed for 11 932 blue sharks measured as part of the Brazilian onboard observer program operating on the pelagic tuna longline fleet between 2006 and 2008, with sizes ranging from 91 to 224 cm fork length. Overall, blue shark size data showed clear spatial and seasonal distributions for males and females in the southwestern Atlantic Ocean, with juveniles predominantly concentrated in the most southerly latitudes.

Excessive phosphorus (P) levels in freshwater aquaculture effluents are a majorenvironmental problem in certain receiving water bodies. This study aimed to test anapproach alternating that alternating feeding P deficient and P sufficient diets andmeasure P loading from rainbow trout (Oncorhynchus mykiss) culture. Threeexperimental practical diets consisting of P-deficient (0.4% P, P04), optimum level of P(0.6% P, P06) and P-sufficient as control diet (0.8% P, P08) were formulated. Sixdifferent feeding regimes of P-sufficient diet continuously (P08), P-deficient dietcontinuously (P04), optimum dietary level of P (P06) continuously, one weekP-deficient/one week optimum level of P diet (P04/P06.1), 2 weeks P-deficient/2 weeksoptimum level of P diet (P04/P06.2) and 4 weeks P-deficient/ 4 weeks optimum level of Pdiet (P04/P06.4) were tested. Fish were fed twice daily to apparent satiation level 16weeks. Fish fed all alternating regimes showed growth rate (weight and length) comparableto those of continuous feeding with P08 and P06 diet. The feed conversion ratios (FCR) forall alternating regimes were comparable to that of the P08 and P06 continuous feedingregime. Neither the thermal unit growth coefficient (TGC) nor condition factor (K)significantly influenced by feeding regimes. Vertebrae P, ash and whole body ash contentdid not differ among regimes. Except fish fed continuous P04 diet, the ash and P contentin opercula and whole body total P content were not significantly different among eachother in a continuous feeding and alternating feeding schedule.

Fish fed all alternating regimes showed significantly lower P consumption than those fedcontinuously fed with P08 and P06. Different feeding regimes had no effect P retention.Significantly higher P loading (solid and dissolved) was noted in fish fed continuouslywith P08 diet, in contrast P loading values were lower for all alternating feedingregimes. The study demonstrated that growth and tissue mineralization of fish maintainedon alternating feeding regimes with P04 and P06 diet were comparable to those continuouslyfed with diet of P08. These results demonstrate that it is possible to reduce P intake by34% and reduce P loading 52% by adopting alternating feeding regimes compared to P08 diet.This study provides evidence that alternating feeding of P deficient and optimum dietarylevels using practical ingredients can be adopted as a means of reducing P loading fromrainbow trout culture without compromising growth.