Time-area closures have become a frequently used tool to control fishing effort and protect feeding and spawning areas. However, because time-area closure strata are mainly based on biological and ecological considerations, and do not accounts for fishermen’s behavior-at-sea, this type of regulation tool may not entirely achieve its objectives. With the aim of comparing the impact of two different time-area regulations: (1) a moratorium on Fish Aggregating Devices (FAD) sets (1997–2005) and (2) a no-take area for surface fleets (2005–2010) on the dynamics of the European (EU) tuna purse seine fleet operating in the eastern tropical Atlantic, several fishery indicators were evaluated through a Before-After, Control-Impact (BACI) approach. The results showed that prior to any regulation, the fleet used to be concentrated within the Gulf of Guinea area. During the first years of the moratorium on FAD (from November to January within a large region in the eastern Atlantic) there was a movement towards outside the protected area, increasing the total sets on FAD (restricted fishing activity). In general, this moratorium fulfilled its objectives; however, it was not respected during the last years of this regulation. The no-take time-area closure restricted all tuna catches for the surface fisheries but only in November and within a small area (i.e., the Picolo zone). As a result, there was an increase in activities on free schools outside the no-take area. Our findings suggest the use of some simple fishery indicators to understand fleet dynamics as a complement of ecological information before implementing new time area closures. Furthermore, since tunas are highly mobile species, anticipating the possible re-allocation of effort of purse seiners to adjacent areas in response to the spatial regulation is required to design different candidate time-area closures and to evaluate their effectiveness to protect juvenile tunas.

The smooth hammerhead shark Sphyrna zygaena (Sphyrnidae) is regularlycaught as bycatch in pelagic longline fisheries, but is one of the least studied of allpelagic sharks. Recently, ICCAT (International Commission for the Conservation of AtlanticTunas) issued recommendations underlining the need for more studies on the life historyparameters of this and other pelagic shark species. To this end, the age and growth ofS. zygaena were studied in the Eastern Equatorial Atlantic Ocean, in anarea where growth parameters were not yet available for this species. Data from 139specimens, caught between June and September 2009, ranging in size from 136 to 233 cm forklength (FL), were analysed. Preliminary trials were carried out to assess the mostefficient growth band enhancement technique. These indicated that sectioning the vertebraeinto 500 μm sections followed by staining with crystal violet producedthe best results. Growth models were fitted using the traditional von Bertalanffy growthequation and a modification of this equation using a known size at birth. Growth modelswere compared using the Akaike information criterion (AIC). The von Bertalanffy growthequation seemed to be the most adequate model to describe growth in this species, withresulting growth parameters of Linf = 272 cmFL, k = 0.06 year for males andLinf = 285 cm FL,k = 0.07 year for females. In the first four years of life, S.zygaena grows 25 cm per year on average, but its growth slows down in laterlife. Future stock assessment models should incorporate these age and growth parametersfor species management and conservation.

The bigeye thresher, Alopias supercilious,is commonly caught as bycatch in pelagic longline fisheries targetingswordfish. Little information is yet available on the biology ofthis species, however. As part of an ongoing study, observers sentaboard fishing vessels have been collecting set of information thatincludes samples of vertebrae, with the aim of investigating ageand growth of A. supercilious. A total of 117 specimenswere sampled between September 2008 and October 2009 in the tropicalnortheastern Atlantic, with specimens ranging from 101 to 242 cmfork length (FL) (176 to 407 cm total length). The A. supercilious vertebraewere generally difficult to read, mainly because they were poorlycalcified, which is typical of Lamniformes sharks. Preliminary trialswere carried out to determine the most efficient band enhancementtechnique for this species, in which crystal violet section stainingwas found to be the best methodology. Estimated ages in this sampleranged from 2 to 22 years for females and 1 to 17 years for males.A version of the von Bertalanffy growth model (VBGF) re-parameterisedto estimate L0, and a modified VBGF using a fixed L0 were fittedto the data. The Akaike information criterion (AIC) was used tocompare these models. The VBGF produced the best results, with thefollowing parameters: Linf = 293 cm FL, k = 0.06 y–1 and L0 = 111 cmFL for females Linf = 206 cm FL, k = 0.18 y–1 and L0 = 93 cm FLfor males. The estimated growth coefficients confirm that A. supercilious isa slow-growing species, highlighting its vulnerability to fishingpressure. It is therefore urgent to carry out more biological researchto inform fishery managers more adequately and address conservationissues.

The amphidromous life cycle and morphological characteristics of Sicydiinae species allowthem to colonise tropical freshwater habitats from the river mouth to the upper reaches ofthe river basin. Otolith microchemistry of 62 Sicydium punctatum from thePérou River, Guadeloupe (French West Indies) was investigated with a femtosecond laserablation-inductively coupled plasma mass spectrometer (fs-LA-ICP-MS) in order toreconstruct individual life history and follow the possible movements of Sicydiumpunctatum after the recruitment. Sr:Ca fingerprint confirmed the amphidromouscycle of this species. Variations of Ba:Ca in some individuals indicated changes inenvironmental conditions after the recruitment in the river. Even if results did not allowconcluding to the specific origin of these variations, the hydrological regime and thebiofilm composition may have a non negligible influence on the Ba availability. Resultssupported the use of multi-elemental signatures in otoliths and highlight the need for alarge geographical and temporal sampling of Ba and Sr in freshwater systems for a betterunderstanding of amphidromous fish species.

Meal frequency is a key parameter in fish larviculture, especially in highlycannibalistic species. Knowledge of the biological bases of cannibalism (growth capacityof cannibals, morphological constraints on cannibalism, prey size preference) can helppredicting the risks of cannibalism for different feeding schedules under cultureconditions. This study relied on the day-by-day analysis of prey size preference andbioenergetics of individual cannibals of the catfish Pseudoplatystoma punctifer(8–65 mm standard length, SL, 0.5–400 mg dry mass,DM) at 28.5 °C under 12L:12D. The results were equated with theontogenetic variations of morphological factors (head and mouth width) and feed efficiencyof larvae feeding on Artemia nauplii, in order to calculate the risks ofcannibalism among fish fed 2–7 daily meals. The predation capacities of P.punctifer were highest at 8 mm SL and decreased in larger fish(largest prey  =  86% and 70% SL in fish of 8 and  >30 mmSL, respectively). Cannibals of increasing size preferred increasinglysmaller prey relative to their own size, but also to their predation capacities. Thesemorphological and behavioural constraints were largely compensated for by bioenergeticsperformance. Cannibals consumed high daily food rations (as high as 171 and 29%DM in fish  <1 and  >300 mg DM,respectively), exhibited high gross conversion efficiencies (0.50–0.55 and about 0.70, infish  <1 and  >30 mg DM, respectively), and grew rapidly(90 and 18% DM day-1 in fish  <1 and  >300 mgDM, respectively). The growth advantage of cannibals over siblings fedArtemia nauplii was decisive, except for high meal frequencies (6–7daily meals). This study supports the view that the risk of cannibalism and adequatefeeding strategies can be largely predicted in a particular fish species if themorphological, behavioural and bioenergetics bases of cannibalism are examined altogetherin an ontogenetic perspective.

This study aims to test the influence of size grading on self-feeding behaviour, socialstructure (measured by the percentage of triggering acts per individual), growthperformances, and blood physiological variables of individually passive integratedtransponder (PIT)-tagged sea bass juveniles, using a computerized on-demand feeding systemcoupled with a PIT tag monitoring device. Three consecutive periods of 27 days each werecompared: a first period (P1) before grading (6 tanks of 100 fish; 40.2 ±  8.9 g) followed by a second period (P2) after grading. The protocolapplied aimed to create two groups of fish of similar mean weight but with either a low ora high coefficient of variation of weight(CVw) corresponding to an imposeddifference in social disruption (Tlow:CVw ~ 10%, 3 tanks of 60 fish each withsocial disruption;Thigh:CVw ~20%,3 tanks of 60 fish each, without social disruption). Tlow andThigh groups were studied over P2, and anadditional 27-day period under identical conditions (P3). The gradingprotocol used and/or time modified the social structure when comparing P1and P2. Thereafter, during P2 and P3,no difference could be observed in growth performances, feed demand, or physiologicalvariables between Tlow andThighgroups. Feeding rhythms and social structures weresimilar in both groups. In conclusion, such grading practice only transiently modifiesfeed demand behaviour and social structure built around the self-feeder, without furtherimprovement in individual growth performances in sea bass.

High levels of larval mortality are a significant barrierto the artificial mass production of Pacific bluefin tuna (Thunnusorientalis). Mortality may occur when larvae sink and comeinto contact with the bottom of the rearing tank during the first10 days after hatching. We evaluated the effect of flow controlby aeration on the survival of T. orientalis larvae.These larvae were held in 500-L tanks in which the aeration ratewas varied during the night. Larval survival increased with airsupply. We documented the cross-sectional flow pattern and gravitationalsinking velocities of larvae to assess the correlation between survivaland circulation patterns in the tank. The sinking velocity of T. orientalis larvaeat night increased with larval body density, which varied with swimbladdervolume. Larvae with uninflated swimbladders sank significantly fasterthan larvae with inflated swimbladders. Both water circulation speedand survival increased at higher aeration rates. Our results suggestthat aeration rates >900 ml min–1 may increase larval survival bycounteracting sinking.

A series of physical characterization methods (UV fluorescence microscopy, X-raymicrodiffraction, backscattered electron imaging and X-ray absorption spectroscopy) wereapplied to Polynesian pearls collected after different cultivation periods, varying fromthree weeks to eighteen months. Through this rigorous time-based sampling, 120 pearlsproduced by 20 different donor oysters were compared. Results show that the structure ofthe pearl layer can be understood as a sequence of distinct secretion processes whoseprogressive occurrence through time may lead to variously arranged and sometimes aberrantmineralized structures. By making comparisons with the structure and growth mode of thePinctada margaritifera shell, this study shows that the currentlyaccepted theory that views the pearl-bed as a “reversed shell” cannot account for thediversity of the microstructural patterns and mineralogical properties observed in thepearl layers. From a practical and economic view point, it appears that development ofthese pre-nacreous materials superposed onto a perfectly round-shaped nucleus is the maincause of shape irregularities in pearls and the consequent decrease in their value.