Sex change of hatchery produced Amphiprion ocellaris: Influence of mating system removal on gonad maturation and nesting success

The influence of gonadal maturation and nesting success of the anemone fish Amphiprion ocellaris was analyzed through mating system removal. Four experiments viz., (i) Sex change of active male to female in the absence of active female, (ii) Juveniles in the presence of a functional male that was changing sex from male to female, (iii) Juvenile in the presence of a functional female, and (iv) Same length group juvenile fishes (total length: 50 mm) without the presence of adult fishes, were carried out. The gonad of male in experiment (i) showed first perceptible sign of sex inversion after 1 to 2 weeks. After 25 weeks the testicular zone almost disappeared and the gonad looked like maturing ovary with perivitellogenic oocytes and oocytes at various stages of development. The gonad of juveniles in the second experiment showed increased testicular development after 23 to 24 weeks, and testicular area became clearly discernible after 30 weeks. In the third experiment, the gonad of juvenile completed its spermatogenesis after 15 to 16 weeks and showed well-developed testicular zones. In the fourth experiment, the gonad of largest fish showed development of ovarian part after 24 weeks with oogonia and oocytes at various stages, and degeneration of testicular tissues. The observation of nesting success in the above experimental groups showed that spawning was obtained in the third group after 4 months of association; and after 12 to 18 months in the first and second groups, and after 20 to 24 months in the fourth group. The present study shows that in the absence or disappearance of adult female, the active male changes sex to female within a period of 25 weeks. The study also confirms that in the clownfish A. ocellaris, the largest and socially dominant fish in a host sea anemone (Heteractis magnifica) is generally female, whose gonads are functional ovaries with remnants of degenerated testicular tissues. The second largest fish in the same group is an active male and has gonad that are functioning testis but also possess non-functioning or latent ovarian cells (ovotestis). If the dominant female dies or is experimentally removed from the "queue", the male not only changes sex but also grows at an accelerated rate, and the juveniles also grow faster to become male and fill the size gap of the social group. This adaptation allows continuous reproduction. It is found that social structure plays an important role on the sex changing mechanism

Isolation, identification and culture of the marine rotifer Colurella adriatica Ehrenberg, 1831 (Family: Lepadellidae) from Andaman & Nicobar Islands: A promising live feed for larval rearing of high value shellfishes and finfishes

An extremely small rotifer was isolated from the micro zooplankton samples collected during February, 2014 from Havelock islands of Andaman and Nicobar Islands. The species was identified as Colurella adriatica Ehrenberg, 1831 (Family: Lapadellidae). Its lorica length under culture period ranged from 47.530 to 98.868 μm and width from 34.308 to 56.277 μm. The size of the eggs, neonates and adults are also documented. Comparison of size of C. adriatica with Brachionus plicatilis (L type) and B. rotundiformis (S and SS type) revealed that C. adriatica is smaller in length and width than the SS-type rotifer which is currently used as a first feed in marine tropical fish larval rearing. However, the larvae of many marine food fishes including groupers and high value marine ornamental fishes are unable to consume the SS-type rotifers as a first feed due to their extremely small mouth gape. The culture of C. adriatica was carried out using Nannochloropsis oculata Diet-I), N. oculata and yeast (0.01g/litre) (Diet-II), Yeast (0.01g/litre) alone (Diet-III). Average population density of C. adriatica with these diets reached a maximum of 1000 nos. of individuals /ml on 10th day of culture on feeding with Diet-I; 950 nos. /ml on 14th day (Diet-II) and 650 nos. /ml on 15th day of culture (Diet-III). Diet I &II and Diet II &III did not show any significant difference (P>0.05) whereas, Diet I and III showed significant difference (P<0.01). Preliminary studies of C. adriatica as a feed to the larvae of Stenopus hispidus, Lysmata amboinensis and Pomacentrus caeruleus showed better survival than larvae fed with B. routundiformis during first phase of larval rearing

Captive Breeding and Seed Production of Marine Ornamental Fishes of India

The marine ornamental fishes are one of the most popular attractions in world wide due to their adaptability to live in confinement. Over the past decade, globally the marine aquarium industry has undergone a significant transformation and this industry is readily growing day by day due to their high commercial value

Spectral refinement with adaptive window-size selection for voicing detection and fundamental frequency estimation

Spectral refinement (SR) offers a computationally in-expensive means of generating a refined (higher resolution) signal spectrum by linearly combining the spectra of shorter, contiguous signal segments. The benefit of this method has previously been demonstrated on the problem of fundamental frequency (F0) estimation in speech processing – specifically for the improved estimation of very low F0. One drawback of SR is, however, the poorer detection of voicing onsets due to the Heisenberg-Gabor limit on time and frequency resolution. This may also lead to degraded performance in noisy conditions. Transitioning between long- and short-time windows for the spectral analysis may offer a good trade-off in these situations. This contribution presents a method to adaptively switch between short- and long-time windows (and, correspondingly, between the short-term and the refined spectrum) for voicing detection and F0 estimation. The improvements in voicing detection and F0 estimation due to this adaptive switching is conclusively demonstrated on audio signals in clean and corrupted conditions

Marine Ornamental Fish Culture – Package of Practices

In recent years, the trade of marine ornamentals has been expanding and it is estimated that 1.5 – 2.0 million people worldwide keep marine aquaria and the value of annual marine ornamental trade is estimated to range between US$ 200 – 330 million. Almost the entire trade is contributed by collections from coral reef habitats which raises doubts regarding its sustainability. The damaging techniques such as use of sodium cyanide are non selective methods used to capture fish and they adversely affect the health of the fish and kill the non target organisms. The over harvesting of target organisms is another aspect of concern. In addition there are high levels of mortality associated with insensitive shipping and poor husbandry practice

Marine ornamental fishes and their breeding: CMFRI initiatives

The marine ornamental fish trade is a sunrise industry in aquaculture and has become a growing industry worldwide. As a result the trade of marine ornamentals has been expanding in recent years and has grown into a multimillion dollar enterprise mainly due to the emergence of modern aquarium gadgets and technologies for setting and maintenance of miniature reef aquaria. Since the marine ornamental trade is operated throughout the tropics, the global marine ornamental trade is estimated at US$ 200- 330 million. Since India is endowed with a vast resource potential of marine ornamentals distributed in the coral seas and rocky coasts with patchy coral formations and the increasing the demand in the domestic trade, it appears very much lucrative for India to venture into this industry

Spawning and larval rearing of Amphiprion ocellaris under captive condition

Marine ornamental fishes have gained much popularity all over the world. India is endowed with a variety of marine ornamental fishes distributed in our coral reef areas which offers vast scope for the development of a domestic as well as export trad