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Details of an egg mass (96 h post-spawn) laid by the pair of Pseudochromis aldabraensis. Embryos are kept together by adhesive threads (AT). At this stage they display large visible eyes and chromatophores (C) in the tail. Scale bar = 500 μm. Top right: the same egg mass, 2.5 cm in diameter, when removed from the PVC pipe guarded by the male.
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The marine aquarium fish industry has been growing rapidly, but still heavily relies on wild-caught organisms. Dottybacks (Pseudochromidae) are among the most popular cultured marine fishes, but issues related to pair formation and filial cannibalism commonly prevent mass production. This study investigated the behavioural aspects of dottyback aqua...
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Context 1
... first successful egg mass hatch, but it was still common for the pairs to occasionally eat them. Many eaten egg masses had a white coloration and no eyespots, indicating poor development. When an egg mass reached day four or five post-spawn, pigmented eyes were visible ( Fig. 2) indicating a readiness to hatch. All hatching events took place when light intensity significantly varied, either when a strong light was positioned above the incubator or 1–2 hours after the lights went out. Egg masses averaged 3 cm in diameter and each contained about 1,200 embryos (Fig. 2). Upon microscopic inspection, adhesive filaments were observed on the surface of all eggs keeping the embryos together. Embryos measured 1.0 mm, while hatched larvae were an average of 3.5 mm in total length. Very few or no chromatophores were visible in the larvae of most species, except for P. aldabraensis and P. paccagnellae larvae, which contained dozens of chromatophores and darker pigmentation when compared to the other species analysed in this study. The pair formation issue in dottyback aquaculture is related to bonding and aggression between the pair. Dottybacks are known to display bi-directional sex change, being able to switch gender back and forth according to either physiological or ecological necessities (Wittenrich and Munday 2005). When pairing dottybacks, it is generally extremely difficult to determine the sex of the individuals; it is very common for same-sex individuals to be placed together. Considering that in many coral reef fishes, aggression is more intense between conspecifics of the same sex (Fricke 1980; Black et al. 2011) due to endocrinal regulation (Oliveira et al. 2002; Black et al. 2011), it is possible that some of our extremely aggressive pairs (e.g. M. splendens ) were not originally heterosexual. Therefore, some pairs might have required sex reversal and the bonding time was correspondingly longer and positively related to aggression level. However, some species demonstrated a trend in aggression level. All pairs of P. fridmani were extremely docile, even when size differed between the individuals (Table 1). Pictichromis paccagnellae pairs, however, demonstrated high levels of aggression throughout. Such trends corroborate the reports of many commercially oriented and non- scientific dottyback breeders (R. Rio, pers. comm.). Most dottybacks are protogynous hermaphrodites and sex reversal in the opposite direction (male to female) can take as much as twice as long and over three months to successfully take place (Wittenrich and Munday 2005; Wittenrich 2007). This may be an explanation for the difference in the time to bond for the two pairs of P. paccagnellae (Table 1). Perhaps pair “A” consisted originally of two males, while pair “B” was either heterosexual or consisted of two females. Time to bond also differed significantly among the P. flavivertex pairs. Considering that P. flavivertex pair “B”, as well as P. fridmani pair “C”, was formed by individuals that spent their entire life cycles together, including larval stages, it is likely that a heterosexual pair was naturally established as juveniles matured. In the case of aggressive broodstock, the internal tank method proved effective in achieving successful pairing and bonding. Another possibility may be stocking several broodstock conspecifics together. Aggressive behaviour will likely occur but the most physically fit heterosexual individuals are also likely to quickly bond and start spawning (Sayadi et al. 2012). Dottybacks readily spawn in captivity if water conditions and feeding regimens are adequate (Wittenrich 2007). It has been reported that dottybacks may start spawning as early as three weeks after bonding (Olivotto et al. 2006). Some of our pairs corroborate such reports, considering that five of 11 pairs spawned within a month after bonding (Table 2). However, other pairs took much longer to start spawning, especially P. paccagnellae pair “B”, spawning only after four months post-bonding. The bonding–spawning interval showed no correlation with time to bond, showing that ...
Context 2
... first successful egg mass hatch, but it was still common for the pairs to occasionally eat them. Many eaten egg masses had a white coloration and no eyespots, indicating poor development. When an egg mass reached day four or five post-spawn, pigmented eyes were visible ( Fig. 2) indicating a readiness to hatch. All hatching events took place when light intensity significantly varied, either when a strong light was positioned above the incubator or 1–2 hours after the lights went out. Egg masses averaged 3 cm in diameter and each contained about 1,200 embryos (Fig. 2). Upon microscopic inspection, adhesive filaments were observed on the surface of all eggs keeping the embryos together. Embryos measured 1.0 mm, while hatched larvae were an average of 3.5 mm in total length. Very few or no chromatophores were visible in the larvae of most species, except for P. aldabraensis and P. paccagnellae larvae, which contained dozens of chromatophores and darker pigmentation when compared to the other species analysed in this study. The pair formation issue in dottyback aquaculture is related to bonding and aggression between the pair. Dottybacks are known to display bi-directional sex change, being able to switch gender back and forth according to either physiological or ecological necessities (Wittenrich and Munday 2005). When pairing dottybacks, it is generally extremely difficult to determine the sex of the individuals; it is very common for same-sex individuals to be placed together. Considering that in many coral reef fishes, aggression is more intense between conspecifics of the same sex (Fricke 1980; Black et al. 2011) due to endocrinal regulation (Oliveira et al. 2002; Black et al. 2011), it is possible that some of our extremely aggressive pairs (e.g. M. splendens ) were not originally heterosexual. Therefore, some pairs might have required sex reversal and the bonding time was correspondingly longer and positively related to aggression level. However, some species demonstrated a trend in aggression level. All pairs of P. fridmani were extremely docile, even when size differed between the individuals (Table 1). Pictichromis paccagnellae pairs, however, demonstrated high levels of aggression throughout. Such trends corroborate the reports of many commercially oriented and non- scientific dottyback breeders (R. Rio, pers. comm.). Most dottybacks are protogynous hermaphrodites and sex reversal in the opposite direction (male to female) can take as much as twice as long and over three months to successfully take place (Wittenrich and Munday 2005; Wittenrich 2007). This may be an explanation for the difference in the time to bond for the two pairs of P. paccagnellae (Table 1). Perhaps pair “A” consisted originally of two males, while pair “B” was either heterosexual or consisted of two females. Time to bond also differed significantly among the P. flavivertex pairs. Considering that P. flavivertex pair “B”, as well as P. fridmani pair “C”, was formed by individuals that spent their entire life cycles together, including larval stages, it is likely that a heterosexual pair was naturally established as juveniles matured. In the case of aggressive broodstock, the internal tank method proved effective in achieving successful pairing and bonding. Another possibility may be stocking several broodstock conspecifics together. Aggressive behaviour will likely occur but the most physically fit heterosexual individuals are also likely to quickly bond and start spawning (Sayadi et al. 2012). Dottybacks readily spawn in captivity if water conditions and feeding regimens are adequate (Wittenrich 2007). It has been reported that dottybacks may start spawning as early as three weeks after bonding (Olivotto et al. 2006). Some of our pairs corroborate such reports, considering that five of 11 pairs spawned within a month after bonding (Table 2). However, other pairs took much longer to start spawning, especially P. paccagnellae pair “B”, spawning only after four months post-bonding. The bonding–spawning interval showed no correlation with time to bond, showing that ...
Citations
... Yet little is known of the early life history of any pseudochromid species in the wild, even though they are very popular aquarium fishes and several species are reared commercially for that trade. All reported species spawn a demersal egg ball, with eggs of about 1-2 mm diameter, which hatch in about 4-5 days into eyed larvae about 2.5-4.5 mm long (Brons, 1996;Olivotto et al., 2006;Mies et al., 2014;Araújo et al., 2016;Madhu et al., 2016). All existing descriptions of larval development in Pseudochromis species are from aquarium aquaculture literature (citations above). ...
Dottybacks (family Pseudochromidae) are small, colorful, important
predators on juvenile fishes on Indo-Pacific coral reefs. Most aspects of their larval ontogeny are little studied. Reared larvae of the orchid dottyback (Pseudochromis fridmani) of 4 to 12 mm body length (BL) were used to document both morphological and swimming ontogeny in 3 cohorts. Development is direct. Larvae are slender, lightly pigmented, lack obvious specializations to pelagic existence, and settle at about 12 mm BL. This morphology is similar to that of several families of
tropical waters including silliganids, scarids, some labrids, and plesiopids. Critical swimming speed (Ucrit) was measured in 85 larvae, which swam at 0.2 to 19 cm/s. In an unplanned comparison, larvae reached greater Ucrit values at 28°C than at 26°C. Only larvae of ≥9 mm BL could swim fast enough to reach an inertial hydrodynamic environment, wherein swimming is likely to be sustainable enough to influence dispersal. However, 60% of larvae of ≥9 mm were unable to do so, and half of these swam in a viscous environment dominated by frictional drag. Results from this study will allow Pseudochromis larvae from field sampling to be identified, may assist studies of pseudochromid relationships, and will help determine the extent to which horizontal swimming of Pseudochromis larvae may influence dispersal and population connectivity and be influenced by temperature.
... In the literature, field study was limited to report the species' distribution, habitat, and morphology [8]. In a captive environment, Mies et al. [22] observed the spawning behaviour and patterns of seven dottyback species for 8 months and reported that the three P. fridmani pairs spawned every 5 to 9 days at 27 • C. Additionally, the authors found that the P. fridmani pairs often cannibalized their own eggs before the first successful hatching occurred, but this filial cannibalism pattern was not quantified over the 8-month period. To date, relevant research data on filial cannibalism of P. fridmani remain scarce, even though this cannibalistic behaviour is considered as an aquaculture bottleneck for P. fridmani as well as many other dottyback species [22,23]. ...
... In a captive environment, Mies et al. [22] observed the spawning behaviour and patterns of seven dottyback species for 8 months and reported that the three P. fridmani pairs spawned every 5 to 9 days at 27 • C. Additionally, the authors found that the P. fridmani pairs often cannibalized their own eggs before the first successful hatching occurred, but this filial cannibalism pattern was not quantified over the 8-month period. To date, relevant research data on filial cannibalism of P. fridmani remain scarce, even though this cannibalistic behaviour is considered as an aquaculture bottleneck for P. fridmani as well as many other dottyback species [22,23]. For the early ontogeny of P. fridmani, Chen et al. [24] and Wittenrich and Turingan [25] documented the development of the digestive system and feeding apparatus of P. fridmani, respectively, while other recent studies focused on optimizing the larval-rearing techniques [24,26,27]. ...
... The P. fridmani embryos were photographed under a dissection microscope (Olympus SZ61, Olympus, Tokyo, Japan) equipped with camera (Olympus DP26, Olympus, Tokyo, Japan). The sampling and observation of embryos occurred every 30 min between 1-5 h PF and at 5,6,7,8,9,10,12,14,16,18,20,22,24,48, and 96 h PF. The embryonic development of P. fridmani was described based on the photographs taken, using stage identification and terminology from Kimmel et al. [33] The newly hatched P. fridmani larvae were cultured in a cylindroconical 100 L fiberglass tank with black walls, connecting to a recirculation system with 25 µm filtration. ...
Aquaculture of marine ornamental fish could potentially reduce the fishing pressure on wild stocks by the global aquarium trade, but its expansion is often constrained by the limited understanding on the biology and early life history of candidate species. The orchid dottyback Pseudochromis fridmani is a valuable and popular marine ornamental fish, but scientific reports on its baseline biology, especially the egg filial cannibalistic behaviour, are scarce. The present study documented key aspects of reproductive biology and early ontogeny of P. fridmani in captivity, including reproductive behaviour, patterns of spawning and filial cannibalism throughout a 12-month period by seven pairs of brood fish, as well as the embryonic and larval development. The results showed that the captive spawning of the broodstock pairs generally occurred every 5–11 days, most commonly every 6–8 days, throughout a year. Despite feeding the brood fish to satiation throughout the data collection period, the average monthly rate of egg filial cannibalism reached 55 ± 37%, but the cannibalism frequency appeared to be pair-specific. The egg incubation duration was approximately 96 h at 27 ± 1 °C, and the development of embryos from cleavage, blastula, gastrula, and segmentation to the pharyngula stage is herein described in detail. The newly hatched P. fridmani larvae possessed important structures and organs for first feeding, including pigmented eyes, developed jaws, and a straight-tube gut. The 0 to 14 days post-hatching (DPH) period appeared to be an important larval stage, as P. fridmani larvae were observed to complete major changes in morphology, gut development, and phototactic behaviour by 14 DPH. Under the culture conditions of this study, the earliest transition to the juvenile stage was observed on 31 DPH, and the majority of fish became juveniles by 56 DPH. The results of this study inform baseline aquaculture production protocols and direct future research, particularly to reduce filial cannibalism through broodstock management and to improve larval culture through supporting the early ontogenetic development of P. fridmani. Additionally, these findings form a foundation for further studying the biology and ecology of P. fridmani in the wild.
... Until the recent modification of criteria and standards for the sustainable use of species of ornamental interest and aquarism (MAPA/SAP 2020), Brazilian legislation has not been efficient in protecting marine ornamental fish through restrictive measures (Sampaio and Ostrensky 2013), where at least 475 fish species and aquatic invertebrates are at risk of extinction (MMA 2018). With the worldwide increase in endangered species (IUCN 2021) and the recent trend of several countries to adopt limitations on the collection of ornamental marine organisms (McClanahan 2011;CITES 2021), an innovative conservation alternative lies in the production in captivity of marine ornamental fish species (Pomeroy et al. 2006;Moorhead and Zeng 2010;Mies et al. 2014;Madhu et al. 2016). ...
The economic feasibility for captive breeding of marine ornamental fish in small spaces is poorly known, especially when considering threatened species. The present study analyzed the economic feasibility for producing Yellow Neon Goby (Elacatinus figaro) (vulnerable) in urban aquaculture systems through different production scenarios: pessimistic, normal, and optimistic, at sales prices of US$ 5.71, US$ 7.62, and US$ 9.52/unit. The financial analysis pointed the total cost of production per animal available to marine ornamental fish trade was between US$ 3.99 and R$ 8.03, with labor and rent as the main expenses. Six of the nine observed schemes showed profitability, including under loss conditions of an entire cycle. The net present value (NPV 8%) reached US$ 83,256 (negative value, unfeasible) until US$ 230,122 (positive value, viable), with profitable conditions presenting an internal rate of return (IRR) ranging from 10.87 to 97.84% and return on capital observed from the first to the sixth year of activity. In addition to the sustainable potential for biodiversity conservation, these results expressed reinforce urban ornamental aquaculture as a profitable instrument for public policy in socioeconomic development at large urban centers and their peripheral regions.
... In contrast, demersal spawners lay eggs on or attached to a substrate, tend to produce fewer eggs, and display a higher level of parental care of eggs (Huntingford et al., 2012). For example, Pseudochromids like the Bicolor dottyback (Pictichromis diadema) spawn demersal egg masses (Mooi, 1990), whereby the male tends to the eggs inside his shelter by providing vigorous oxygenation and tumbling (Mies et al., 2014). Developmentally, demersally spawned larvae tend to be competent with functional jaws and pigmentation in the eyes, the yolk sac is almost exhausted, and mouths and digestive tracts are open and functional (Huntingford et al., 2012). ...
An average of 7.6 M individual fishes, representing 1.8 K species from 125 distinct fish families, are imported into the U.S. annually for the marine aquarium trade. While many wild-caught species are traded annually, there are only ~39 commercial aquaculture businesses in the U.S. (2020), and 96 species commercially available as aquacultured. This study presents a data-driven framework to empower the selection of species to target for aquaculture research and development. The framework is based on species-specific data for 105 of the top 130 species imported into the U.S., including market characteristics (aquarium suitability, number of imports, retail price), aquaculture practicality (demersal/pelagic spawning strategy, pelagic larval duration, size at hatch), and conservation assessment (aquacultured status, ecological niche, geographic distribution, and mid-depth). A principal component analysis revealed that fish species which feature life history characteristics conducive to practical aquaculture efforts also either 1) demonstrate favorable market characteristics, or 2) are vulnerable to overfishing and thus merit the effort from a conservation perspective. Conversely, fish species whose life history characteristics render them challenging to aquaculture also either 1) demonstrate less favorable market characteristics, or 2) also demonstrate life history characteristics that equip them with resiliency to overfishing and thus may best be prioritized for wild collection under sound fisheries management.
... Within Pomacentridae, clownfish are protandric hermaphrodites (Iwata, Nagai, Hyoudou, & Sasaki, 2008;Olivotto & Geffroy, 2017) and damselfish are typically protogynous hermaphrodites, although there are gonochorist species (Fishelson, 1975;Shei et al., 2017;Wittenrich, 2007). Dottybacks (Pseudochromidae) are sequential hermaphrodites, with most species being protogynous and some displaying bidirectional sex change (Kuwamura, Kadota, & Suzuki, 2015;Mies, Güth, Scozzafave, & Sumida, 2014;Wittenrich & Munday, 2005). Gobiids exhibit a large variety of sexual patterns, with gonochorism and both forms of sequential hermaphroditism reported in many genera (Wittenrich, 2007;Munday, Kuwamura, & Kroon, 2010;Herler et al. ...
... Blenniidae and MOFA aquaculture are still early in their development. The reproductive biology of the main aquacultured species, including clownfish, dottybacks, and gobies, is reasonably well known, and specific and successful protocols have been established for broodstock formation and pairing (Mies et al., 2014;Shei et al., 2017;Wittenrich, 2007). However, there is no such protocol for blennies. ...
The marine aquarium industry has grown significantly and so has marine ornamental fish aquaculture. The main species targeted by commercial aquaculture are clownfish, dottybacks, gobies, and blennies. However, the limited knowledge available for the reproductive biology of several fish species hinders production, especially for blennies. Therefore, this study investigated whether two mass‐produced blenniids, Meiacanthus nigrolineatus and Meiacanthus smithi, are gonochorists and display caudal fin sexual dimorphism. For this purpose, gonadal samples and morphometric data were collected from specimens of both species kept in captivity for 6 months. Histological preparations of the whole individuals or their gonads were performed and analyzed. Results show that sex ratio does not differ from 1:1 and that gonadal development was similar to other blenniids. No evidence of sexual reversion or simultaneous hermaphroditism was found in the first 8 months of development, suggesting that both species are gonochoric. Differences in the length of upper and lower rays in the caudal fin were not detected for M. smithi, but M. nigrolineatus male individuals displayed significantly longer upper and lower rays, confirming it as a dimorphic trait for this species. The identification of the sexual pattern and sexually dimorphic traits may aid in broodstock pairing for M. nigrolineatus blennies, improving its aquaculture production and perhaps reducing some of the pressure on wild stocks.
... The two most common spawning modes for teleost fish are demersal and pelagic spawning (Olivotto et al. 2011a). Demersal spawners usually attach their eggs to substrates or release gelatinous eggs in small caves, and males or both parents show parental care, such as guarding, fanning and removing dead eggs, before hatching occurs (Madhu et al. 2012a;Mies et al. 2014;Olivotto et al. 2017b;Majoris et al. 2018). Examples of demersal spawners among popular marine ornamental fish include goby (Gobiidae), damselfish (Pomacentridae), blenny (Blenniidae) and dottyback (Pseudochromidae) ( Table 1). ...
... Unfortunately, in more cases, the fish gender is difficult to distinguish morphologically. Indeed, sexual dimorphism is often very ambiguous or virtually absent for many ornamental fish, such as those from the families of Acanthuridae (surgeonfish; Emel'yanova et al. (Emel'yanova et al. 2009a(Emel'yanova et al. , 2009b and Pseudochromidae (dottyback; Mies et al. 2014). For instance, inconspicuous difference in papilla morphology at the urogenital area was reported as the only sexual dimorphism of several reef fish even under close examination (Emel'yanova et al. 2006;Emel'yanova et al. 2009b). ...
... For species with little sexual dimorphism, their gender may become distinguishable after the bond is formed between a broodstock pair. For example, female fish usually exhibit a swollen belly prior to spawning (Leu et al. 2010;Madhu & Madhu 2014;Mies et al. 2014; Degidio et al. 2017; Majoris et al. 2018), but this feature can only be seen after females successfully reach sexual maturity. Difference in behaviour in a broodstock pair could also help differentiate the gender of individual fish. ...
Marine ornamental fish are a key component of the multimillion‐dollar marine aquarium trade industry, a controversial industry due to current heavy reliance on wild‐collected specimens. Aquaculture of marine ornamental fish is considered as a sustainable alternative, but it is still in the early stage of development. This review focuses on the current state of marine ornamental fish aquaculture, by covering topics on reef fish reproductive biology in captivity, traditional and novel live feeds, feeding regimes and visual environment in larviculture. Where possible, major differences between demersal and pelagic spawners are compared and discussed. Overall, for many ornamental fish species, natural spawning can be achieved in a captive environment without the use of hormone induction; however, sex identification and successful pairing for reef fish species could be a challenge. With the use of both traditional (rotifers and Artemia) and novel live feeds (e.g. marine copepods and ciliates), a range of breakthroughs in larval rearing of both demersal and pelagic spawning ornamental fish species have been achieved in recent years, although larval survival varies. To further improve the larval rearing success of marine ornamental fish, this review suggests that future research should focus on optimizing the use of live feed in terms of both quality and quantity, and establishment of well‐defined species‐specific larval feeding regime, as well as providing appropriate rearing condition through improved manipulation of light conditions and the ‘greenwater’ techniques in larval rearing.
... The marine aquarium fish industry has been growing rapidly (Olivotto et al. 2011), but still heavily relies on wildcaught individuals (Mies et al. 2014). Maximised exploitation of clownfish exemplars and improved cultivation protocols for commercial-scale production are essential for greater economic gain in aquaculture of ornamental marine fish. ...
The objective of this study was to evaluate the effect of different diets on sexual differentiation and growth of mature couples of clownfish (Amphiprion ocellaris). Three commercial diets and one experimental diet (in triplicate) were used: OTH (Otohime®); ALC (Alcon®); NRD (INVE-NRD®); and ED (experimental diet). To determine sexual differentiation, the larger individual was considered female and the smaller male. Once the diet was provided, biometric parameters (weight and length) of the formed couples were evaluated daily, to determine the duration of sexual differentiation. The duration of sexual differentiation was significantly longer in clownfish fed the NRD diet compared to the OTH and ALC diets (P<0.05). In conclusion, the duration of sexual differentiation of clownfish was influenced by diet.
Demersal spawning and mouthbrooding species comprise more than 70% of the production of marine ornamental fish. Apart from clownfish, there are several families of demersal spawners that are cultured for the ornamental trade, including gobies, blennies, dottybacks, damselfish and others. These species are characterized by producing eggs that are deposited on a substrate. The eggs are tightly packed together and may be adhered to the substrate or simply laying on it. Most ornamental demersal spawners display parental care during embryonic development and this feature is critical for successful hatching. Mouthbrooders, on the other hand, orally incubate the embryos before hatching. Newly hatched larvae of demersal spawners and mouthbrooders typically have very little yolk and are able to feed immediately after hatching. Live feeds such as rotifers and brine shrimp nauplii are frequently offered, but additional food sources including wild zooplankton, copepods and ciliates can be essential for successful mass production of some species.
