Octopus Maya Research Articles

Two new species of dicyemid mesozoans (Dicyemida: Dicyemidae) from Octopus maya Voss & Solis-Ramirez (Octopodidae) off Yucatan, Mexico.

Two new dicyemid species are described from the endemic cephalopod Octopus maya Voss & Solis-Ramirez collected off Yucatan, Mexico. The renal sacs of 40 juvenile and adult octopuses from four localities were examined. Dicyema hochbergi n. sp. is a medium-sized species that reaches 2,245 µm in length. The vermiform stages consist of 18-24 peripheral cells, a conical calotte and the extension of the axial cell between the base and middle of the metapolar cells. Infusoriform embryos consist of 39 cells with urn cell containing one germinal cell, two nuclei and solid refringent bodies. Dicyema mexcayae n. sp. is a relatively small species that reaches 1,114 µm in length. The vermiform stages are constituted by 14-16 peripheral cells, an elongate calotte and the axial cell extending forward to the middle of the metapolar cells. The infusoriform embryos consist of 37 cells, two solid refringent bodies and urn cells with two nuclei each. The present study represents the first description of a dicyemid species from O. maya and increases the number of described species from Mexican waters to 11.

Quality indicators and shelf life of red octopus (Octopus maya) in chilling storage

There are no precedents concerning the quality of Octopus maya during chilled storage. This study evaluated the shelf life of the red octopus in chilling storage (4oC) and the correlation of the sensory quality index with microbiological counting and the biochemical indicators (hypoxanthine, histamine and volatile amines). A total of 112 whole raw octopi (average weight of 896 g) were randomly selected from seven batches and exposed to 4°C for 18, 24, 48, 72, 84, 96, and 100 h. The histamine concentration (91.7%), followed by the counts of psychrotrophic bacteria (5.5%) and hypoxanthine (2.2%), were the predictors from the redundancy analysis that better explained the changes taking place during the chilling hours. After 72 h of chilling, the microbial count was determined to be log 4.7 CFU/g, and the octopus samples were classified as B quality (minor sensory quality defects) based on the sensory quality scale. Although the samples were not classified as unacceptable at 100 h of refrigeration by the sensory index, the level of histamine reached the defect action level (5 mg/100 g) as ruled by the International Food Safety Authorities. The shelf life of the red octopus in chilling storage was predicted to be 119 h.

Chemical Tools of Octopus maya during Crab Predation Are Also Active on Conspecifics.

Octopus maya is a major socio-economic resource from the Yucatán Peninsula in Mexico. In this study we report for the first time the chemical composition of the saliva of O. maya and its effect on natural prey, i.e. the blue crab (Callinectes sapidus), the crown conch snail (Melongena corona bispinosa), as well as conspecifics. Salivary posterior glands were collected from octopus caught by local fishers and extracted with water; this extract paralyzed and predigested crabs when it was injected into the third pereiopod. The water extract was fractionated by membrane ultrafiltration with a molecular weight cut-off of 3kDa leading to a metabolic phase (>3kDa) and a neurotoxic fraction (<3kDa). The neurotoxic fraction injected in the crabs caused paralysis and postural changes. Crabs recovered to their initial condition within two hours, which suggests that the effects of the neurotoxic fraction were reversible. The neurotoxic fraction was also active on O. maya conspecifics, partly paralyzing and sedating them; this suggests that octopus saliva might be used among conspecifics for defense and for reduction of competition. Bioguided separation of the neurotoxic fraction by chromatography led to a paralysis fraction and a relaxing fraction. The paralyzing activity of the saliva was exerted by amino acids, while the relaxing activity was due to the presence of serotonin. Prey-handling studies revealed that O. maya punctures the eye or arthrodial membrane when predating blue crabs and uses the radula to bore through crown conch shells; these differing strategies may help O. maya to reduce the time needed to handle its prey.

Reproductive traits of Octopus maya (Cephalopoda: Octopoda) with implications for fisheries management

ABSTRACTOctopus maya is the main species caught in Mexico. From September 2007 to June 2008, its sex ratio, reproductive season, frequency of non-vitellogenic and vitellogenic oocytes, reproductive indices, and size and weight at maturity, were evaluated. The monthly sex ratio was significantly different from 1:1. The major reproductive season occurs during February to June (dry season) in Yucatan. May−June is the common reproductive season to both Yucatán and Campeche populations. Higher frequencies of vitellogenic oocytes (> 50%) were found from January-March and in May. From five reproductive indices, only the macroscopic and microscopic maturity indices were the best descriptors of the reproductive season in females, whilst only the reproductive complex index was the best descriptor in males. The weight at sexual maturity (BW50%) was 335 g for females and 242 g for males. The size at sexual maturity (DML50%) was 12.58 cm for females and 7.42 cm for males. It is recommend revising the minimum catch size by following these results. The reproductive traits here evaluated could contribute to the recently created Plan for Management of Octopus Fisheries, in particular action line no. 1.4, which refers to protection of females during breeding, and to their protection throughout the entire reproductive season.

In vitro acid digestibility of four marine species using the digestive gland of adult Octopus vulgaris.

In vitro acid digestibility of four marine species using the digestive gland of adult Octopus vulgaris.

Timing of digestion, absorption and assimilation in octopus species from tropical (Octopus maya) and subtropical-temperate (O. mimus) ecosystems

Culture of octopuses is still in an experimental stage due to a lack of knowledge about their digestive physiology. This study aimed to determine the temporality of nutrient digestion, absorption and assimilation in 2 species of octopus: the tropical Octopus maya (habitat temperature 22 to 26°C) and the subtropical-temperate O. mimus (15 to 21°C). In both species, the chyme volume displayed 2 peaks over time along the digestive tract: one at the beginning of digestion and a second at the end of the digestion process. These phases were observed in gastric juice (GJ) enzymes, in the flow of nutrients in the digestive gland (DG), in the appearance of metabolites in the hemo lymph, and in muscle protein and glycogen levels. The soluble nutrient flow throughout the digestive tract into the DG was similar in both species. How ever, intracellular digestion was different in O. mimus compared to O. maya; lipids were mobilized faster than proteins in O. mimus, whereas proteins were mobilized faster than lipids in O. maya. This suggests that at low temperatures, the mobilization of lipids could be a biological priority due to their role in membrane protection. In addition, O. mimus displayed more digestive enzyme activity in the GJ and DG compared with O. maya, suggesting that adaptive differences may be related to environmental temperatures.

Effect of maternal temperature stress before spawning over the energetic balance of Octopus maya juveniles exposed to a gradual temperature change

Octopus maya supports an important fishery in Yucatan Peninsula (YP) where this species is highly abundant. Considering that temperatures in the tropics are increasing (IPCC, 2013), there are several scenarios that can modify the dynamic of the O. maya population in YP: i) prolonged summer and short winter seasons, and/or ii) fast temperature increases and high temperatures after a winter season, both affecting the survival of hatchlings and the performance of juveniles. The present study was designed to evaluate the effect of maternal temperature stress over hatchling and juvenile performance in terms of their energetic plasticity and thermoregulatory behaviour, when they were exposed to a gradual temperature increase (TI) from 24 to 30°C and compared with hatchlings maintained at preferred and constant temperature (24°C). Hatchlings from stressed females were smaller, and had a lower growth rate compared to those from unstressed females providing evidence that temperature stress experienced by females has consequences on the performance of hatchlings, with effects on the biomass production and survival. Results also demonstrated that hatchlings exposed to TI (24–30°C) had a growth rate and oxygen consumption similar to those maintained at preferred temperature (24°C), in both female groups indicating that a gradual temperature increase of 1°C every 5days is probably enough to allow the organisms to make physiological adjustments without an excessive energetic cost.

Advances in the Octopus maya digestive physiology

Red octopus ( Octopus maya ) is an important fishery resource in Mexico, due to its high commercial value and domestic and foreign demand. An alternative to fishing is the mariculture. Cephalopods digestion is a two-part process: extracellular and intracellular. This paper describes the progress made in Octopus maya digestive physiology study, particularly, in the digestion temporality, absorption and assimilation of crab in an attempt to assess the nutrients dynamic and usage along the digestive tract and, how these are transported, stored and used as an energy source for growth.

Thermal biology of prey (Melongena corona bispinosa, Strombus pugilis, Callinectes similis, Libinia dubia) and predators (Ocyurus chrysurus, Centropomus undecimalis) of Octopus maya from the Yucatan Peninsula

On the Yucatan Peninsula there is an upwelling which allows access to a body of cold water that controls temperature in this area. This modulates the ecology and distribution of organisms that inhabit the continental shelf. The objective of this study was to determine the effect of different acclimation temperatures on the thermal biology of prey as mollusc, crustacean (Melongena corona bispinosa, Strombus pugilis, Callinectes similis, Libinia dubia) and predators as fish (Ocyurus chrysurus, Centropomus undecimalis) of Octopus maya. Octopus prey preferred temperatures between 23.5°C and 26.0°C, while predators preferred temperatures 26.4–28.5°C. The species with largest thermal windows were M. corona bispinosa (328.8°C2), C. similis (322.8°C2), L. dubia (319.2°C2), C. undecimalis (288.6°C2), O. chrysurus (237.5°C2), while the smallest thermal window was for S. pugilis (202.0°C2). The acclimation response ratios (ARR) estimated for prey ranged from 0.24–0.55 in animals exposed to CTMax and 0.21–0.65 in those exposed to CTMin. Amongst predators, ARR ranged from 0.30 to 0.60 and 0.41 to 0.53 for animals exposed to CTMax and CTMin, respectively. Correlating the optimal temperature limits of prey and predators with surface temperatures on the continental shelf and those 4m deep showed that the main prey, Callinectes similis and L. dubia, shared a thermal niche and that an increase in temperature could force these species to migrate to other sites to find optimal temperatures for their physiological functions. As a consequence the continental shelf community would undergo a structural change. Predators were found to be near their optimal temperatures in surface temperatures on the continental shelf. We conclude that they would remain in the area in a warming scenario.The size of the thermal window was related to the type of ecosystem inhabited by these species. These ARR intervals allowed us to categorize the species as temperate or tropical, according to the oceanographic conditions that prevail on the Yucatan Peninsula.

Effects of temperature on embryo development and metabolism of O. maya

Octopus maya is one of the most promising candidates for octopus aquaculture due to its holobenthic development. The objectives of this study were to investigate: i) whether the time required for embryonic development of this species can be reduced; ii) whether high or low temperatures affect the size and physiological characteristics of embryos; iii) whether temperature affects the time taken to reach stage XX, using thermal time; and iv) the effects of incubation temperature on hatchling performance, measured as survival after 10 d fasting. Eggs were acclimated at 18, 22, 26 and 30°C. Embryos incubated at 30°C reached stage XX 50 d before embryos incubated at 18°C. A mean value of 596 degrees day−1 was obtained for embryos incubated at 22 and 26°C where embryo development was optimum. Principal component analysis showed that arm length was the morphological characteristic that separated embryos incubated at 22°C from the rest of the treatments. Embryos in stage XIX and incubated at 26°C had a higher metabolic rate than embryos maintained at other experimental temperatures. The best hatchling performance was obtained with embryos incubated at 22°C. Results indicated that the optimal temperature for O. maya incubation is in the range of 22–26°C. Statement of relevanceOctopus maya is one of the most promising species for octopus aquaculture due its holobenthic development. This study will be useful when design production facilities because it gives key information to obtain the hatchlings with the best performance.

Spatial Analysis of the Abundance and Catchability of the Red OctopusOctopus maya(Voss and Solís-Ramírez, 1966) on the Continental Shelf of the Yucatan Peninsula, Mexico

The red octopus Octopus maya is an endemic species of the continental shelf of the Yucatan Peninsula, Mexico and supports the largest octopus fishery in the American continent. Little is, however, known about its spatial dynamics. The study of the space-time variation of catchability is a key element in the stock assessment, because it allows behavioral aspects of the resource and qualities of the various exploitation strategies to be clarified, which are essential for the fishery management. The objective was to analyze the spatio-temporal variations of the abundance and catchability of the octopus O. maya on the continental shelf of the Yucatan Peninsula, Mexico. During the fishing season of 2012 (August–December), fishery landings from the small-scale fleet in 13 ports of the Yucatan Peninsula, were analyzed to obtain data on catch, effort and fishing zone for O. maya. During the closed season of 2013 (January–July) fishing hauls were performed across a network of stations along the coast of the Yucatan Peninsula. Spatio-temporal variations in mean catch per unit effort (CPUE) in terms of number of organisms per hour of effective fishing were analyzed. Catchability and its variation with size, time, and zone were estimated through a model based on the Leslie transition matrix and frequency distributions of mantle length. The results showed significant changes in the distribution of O. maya. During the fishing season, the greatest abundances were found along the coast of Campeche (western zone), whereas, during the closed season the highest abundances were recorded along the coast of Yucatan (eastern zone). Trends of decreasing and increasing catchability were observed with respect to size according to the different zones. A high catchability was presented for small sizes along the coast of Campeche during the fishing season. The results indicate the need to investigate possible management measures differentiated by region (west-east) to ensure the fishery sustainability.

Seasonal changes of progesterone and testosterone concentrations throughout gonad maturation stages of the Mexican octopus, Octopus maya (Octopodidae: Octopus)

Variations in progesterone (P4) and testosterone (T) levels in the gonad of Octopus maya from Sisal in Yucatan State, Mexico, were investigated by radioimmunoassays and in relation to four gonad maturation stages (GMS) and to the reproductive cycle, as represented by two maturity indices (microscopic ‘MiMI’ and macroscopic ‘MaMI’). According to the GMS and the maturity indices, the reproductive season of O. maya from Yucatan occurred from February to June. In females, P4 and T displayed the same pattern, with a tendency to increase at the same time, although on average, P4 had seven-fold higher concentrations than T. In contrast, P4 and T in male gonads displayed a different pattern, where T concentrations were relatively stable throughout all of the study months. In the female gonad P4 was lowest (close to 0 pg g–1) during both developing (GMS-I) and maturing (GMS-II) stages, and increased (189 ± 53 pg g–1) approaching the mature stage (GMS-III) to a maximum value of 611 pg g–1. Concentrations of T in the male gonad were lowest (106 ± 9 pg g–1) during the maturing stage (GMS-II) and increased up to the mature stage (GMS-III), reaching a maximum of 440 pg g–1. Pearson's correlation (r) between hormones and maturity indices showed strong relationships for females (around 0.4 and −0.7; p < 0.05), but there were negligible or weak relationships for males (0.2 and −0.1; p > 0.05). Hormone correlations in females were inverse with MaMI and direct with MiMI. Our major findings showed that gonadal P4 levels were elevated during GMS-III and GMS-IV (i.e. periods of vitellogenic oocytes), where the characteristic aspect is an ovary with very high oocyte diameters, with the primary follicle cells deeply infolded in the ooplasm for yolk synthesis. These results suggested a synchrony between P4 and the process of folliculogenesis, and in turn, vitellogenesis.

Effects of parental diets supplemented with different lipid sources on Octopus maya embryo and hatching quality

Abstract The present research showed, for the 1st time, the effect of formulated diets for broodstock of Octopus maya . Reproductive response of O. maya females fed prepared diets and a control diet (crab) was evaluated according to reproductive performance and hatchling quality. Females were fed three formulated most diets based on: 1) crab and squid (CS), 2) crab, squid and fish heads (CSF) and 3) crab, squid and SELCO ® (CSS). Fresh crab ( Callinectes sapidus ) (Diet 4, C) was used as a control diet. A total of 10 females were used for each experimental diet (n = 40). Females were fed 5% body weight d − 1 until spawning. The feeding period of females was 50 days on average to natural spawning (p 0.05) in soluble protein content of the perivitelline or newly hatched survival after 10 days unfed. Morphometric differences on 40 days old embryos were associated with females (p 0.05). Results obtained indicate that O. maya female's present marked adaptation to the diets ingested prior to egg laying, without compromising reproductive performance. Statement of relevance Advances in diets to Octopus maya reproduction.

Is temperature conditioning Octopus maya fitness?

Temperature is a key factor that modulates Octopus maya reproduction. Evidence shows that wild females spawn when ambient natural temperatures are lower than 26°C, caused by either the winter sea temperatures or the upwelling events. The upwelling determines the availability of cold and nutrient rich water during spring and summer in the northern side of the Yucatán Peninsula (YP). We determined the effects of ambient temperature on the reproductive performance of female O. maya maintained in thermal regimes that simulate (a) high summer temperature at the eastern side of the YP (31°C), (b) winter temperature in all the YP (24°C), and (c) a temperature decrease (TD) at a rate of 1°C/5d from 31 to 24°C. The number of spawns, eggs spawned by female, fertilization percentage, embryos development, and hatchlings survival after starvation were evaluated for each thermal regime. At 31°C spawning of O. maya females is inhibited; only 13% spawned. The few fertilized eggs spawned died after two 2weeks, indicating that high temperatures are deleterious to embryos. Females exposed to temperature changes of 1°C/5 d spawned only after temperature reached below 27°C, 87% of the females spawned. At the end TD treatment a mean value of 530 eggs per spawn was observed. Fertilization of spawns was around 50%. All the females maintained at 24°C spawned a mean of 1208 eggs/spawn with a 70.5% fertilization rate. Embryonic development was interrupted early in TD treatments causing premature hatchlings by day 31. These premature juveniles showed smaller sizes and low survival (48%) after a 10-day fast. In contrast, embryos spawned at 24°C exhibited larger development (45d), and hatchlings survival after a 10-day fast was 100%. Our results explain why O. maya spawns are limited to winter in the western side of the YP, when temperatures drop due to polar winds. Results also highlight the importance of the Yucatan upwelling for maintaining suitable conditions for spawning, embryo development, and hatchling survival along the year at Eastern border of the YP. We consider that this species could be negatively affected if climate change leads to an ocean warming scenario.

Effects of maternal diet on reproductive performance of O. maya and its consequences on biochemical characteristics of the yolk, morphology of embryos and hatchling quality

Abstract This study examined the effects of mixed diets (with the crab Callinectes spp. as the main component of the diet) on embryonic development and hatchling quality of Octopus maya . Several O. maya females were fed one of 4 different diets being 1) crab, 2) crab and squid, 3) crab and mussel and 4) crab and fish heads, in a 7:3 ratio. The effects of each diet on the reproductive performance were evaluated by quantifying the total number of eggs female − 1 , eggs clutch − 1 , hatchlings female − 1 , hatchling weight and hatchling quality, measured as the hatchling survival after 10 days of fasting. In addition, the chemical characteristics of the diet were studied through determination of proximal analysis, amino acid and fatty acid profiles, its relation to the chemical characteristics of the yolk and the morphological characteristics of embryos. Results indicate that mixed diets delivered embryos with a combination of nutrients that promoted a better performance, compared to those from females fed crab exclusively. Females fed mixed diets apparently used energetic amino acids (AAs) to synthesize yolk, which play essential roles in embryo metabolism. In addition, females fed mixed diets used saturated and polyunsaturated fatty acids (FAs) in the diet to provide yolk with a combination of FAs that allowed hatchlings a better performance during the first days of culture. Mixed diets used in the present study could have the nutritional components to satisfy nutritional requirements for reproduction in this octopus species.

Octopus lipid and vitamin E composition: interspecies, interorigin, and nutritional variability.

Octopus vulgaris, Octopus maya, and Eledone cirrhosa from distinct marine environments [Northeast Atlantic (NEA), Northwest Atlantic (NWA), Eastern Central Atlantic, Western Central Atlantic (WCA), Pacific Ocean, and Mediterranean Sea] were characterized regarding their lipid and vitamin E composition. These species are those commercially more relevant worldwide. Significant interspecies and interorigin differences were observed. Unsaturated fatty acids account for more than 65% of total fatty acids, mostly ω-3 PUFA due to docosahexaenoic (18.4-29.3%) and eicosapentanoic acid (11.4-23.9%) contributions. The highest ω-3 PUFA amounts and ω-3/ω-6 ratios were quantified in the heaviest specimens, O. vulgaris from NWA, with high market price, and simultaneously in the lowest graded samples, E. cirrhosa from NEA, of reduced dimensions. Although having the highest cholesterol contents, E. cirrhosa from NEA and O. maya from WCA have also higher protective fatty acid indexes. Chemometric discrimination allowed clustering the selected species and several origins based on lipid and vitamin E profiles.

Growth, survival and physiological condition of Octopus maya when fed a successful formulated diet

Abstract A formulated diet for Octopus maya that provoked a growth rate and survival higher than that observed when animals were fed diet based only on freeze-dried crab is reported for first time. Early juveniles (0.37 g wet weight; ww) of O. maya were used. Diets were made by mixing freeze-dried ingredients (crab paste; Callinectes spp. meal; (Cr), squid meal; Dosidicus gigas (Sq) and silages (Si)) all enriched with a mix of vitamins and minerals, and bound with gelatin, forming a paste. At the end of the experiment, Crab–Squid (CrSq) was the only diet that showed 100% survival, followed by Crab (Cr) (55%). The highest specific growth rate (SGR, % day − 1 ) was obtained in animals fed CrSq (3.04% day − 1 ) followed by animals fed Cr (1.96% day − 1 ) and Squid (Sq) (1.09% day − 1 ). Marginal (0.36% day − 1 ) and negative (− 0.73% day − 1 ) SGR values were observed in animals fed Silage–Crab–Squid (SiCrSq) and Silage–Squid (SiSq). Principal component analysis (PCA) showed that muscle glycogen and DG protein contents had the strongest influence on the separation of groups in a canonical analysis and were positively related with growth indicating that CrSq diets have the best nutritional characteristics to satisfy growth requirements. These results were confirmed when energy balance was measured.

Can preference for crabs in juvenile Octopus maya be modified through early experience with alternative prey?

Previous studies on cephalopod feeding have suggested that predetermined preference for certain prey types can be modified by exposing newly hatched individuals to visual or chemical stimuli (imprinting), or by familiarizing them to feed on prey different from those preferred (associative learning). The aim of our study was to determine whether preference to attack crabs in Octopus maya could be modified by early experience with or without food reinforcement using palaemonid shrimp, a prey octopuses consume readily, but will reject if crabs are available. We conducted experiments on the attack response of juvenile octopuses that had been either exposed to (visual and chemical stimuli for at least 48 h before and after hatching) or had fed only on palaemonids (16 days after hatching). Octopuses were then presented with crabs and palaemonids simultaneously and attacks on either prey were recorded. Control treatments, where octopuses had to choose between two similar alternatives (no choice) were included in order to discriminate between active and passive selection. Results were analysed by means of asymmetrical contingency tables. Both, octopuses that had only been exposed to stimuli from palaemonids and those that fed on shrimp, selectively attacked crabs when first presented with both alternative prey ( and , respectively; both ). These results indicate that preference for crabs in early juvenile O. maya could not be modified through experience with other prey. Because octopuses had never been in contact with crabs prior to trials, such preference was not obtained through their short life experience but could be pre-determined.

Effects of Different Prey and Rearing Densities on Growth and Survival of Octopus Maya Hatchlings

The present study aims to determining the isolated and combined effects of stocking and prey densities on growth and survival of Octopus maya hatchlings both at experimental level and in a pilot scale system (8 m2; 2700 L). Octopus survival was not related to prey density. Gained wet weight resulted in a significant interaction between initial stocking density and prey density indicating that octopus growth under low and high density was affected in a different manner depending on the density in which prey were offered. Prey density did not have a significant effect on growth and octopus fed with all three prey densities gained wet weight in a similar way. Results indicate the use of culture densities of 140 octopus m-2, and at least 0.27 g prey octopus-1 d-1 can be used to cultivate octopuses in small tanks. In tanks of 8m2 a higher growth rate was obtained with both 25 and 50 octopus m-2 densities were used. Survival was not affected by stocking density between 25 to 75 octopus m-2.

Chapter One - Cephalopod Culture: Current Status of Main Biological Models and Research Priorities

A recent revival in using cephalopods as experimental animals has rekindled interest in their biology and life cycles, information with direct applications also in the rapidly growing ornamental aquarium species trade and in commercial aquaculture production for human consumption. Cephalopods have high rates of growth and food conversion, which for aquaculture translates into short culture cycles, high ratios of production to biomass and high cost-effectiveness. However, at present, only small-scale culture is possible and only for a few species: the cuttlefish Sepia officinalis, the loliginid squid Sepioteuthis lessoniana and the octopuses Octopus maya and O. vulgaris. These four species are the focus of this chapter, the aims of which are as follows: (1) to provide an overview of the culture requirements of cephalopods, (2) to highlight the physical and nutritional requirements at each phase of the life cycle regarded as essential for successful full-scale culture and (3) to identify current limitations and the topics on which further research is required. Knowledge of cephalopod culture methods is advanced, but commercialization is still constrained by the highly selective feeding habits of cephalopods and their requirement for large quantities of high-quality (preferably live) feed, particularly in the early stages of development. Future research should focus on problems related to the consistent production of viable numbers of juveniles, the resolution of which requires a better understanding of nutrition at all phases of the life cycle and better broodstock management, particularly regarding developments in genetic selection, control of reproduction and quality of eggs and offspring.