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Reproduction of hatchery-produced meagre (Argyrosomus regius) in captivity: effects of GnRHa implants on sperm quality

Biglino, Tommaso (2015) BION01 20141
Degree Projects in Biology
Abstract
Aquaculture is a growing sector and many studies are carried out to select and optimize species for conservation, keeping or production. Lately, new species are being introduced in aquaculture, although for some of them the basic knowledge is still incomplete. Moreover, there are further issues connected to acclimatising the new species to artificial conditions and have them reproduce successfully. Studies on one of those new species, meagre (Argyrosomus regius), are still on early stages and females are usually the preferred test subjects. Reproduction in captivity, though, needs to be analysed also from the male point of view to have a complete image of the possible problems and solutions available to have a successful spawning. So far,... (More)
Aquaculture is a growing sector and many studies are carried out to select and optimize species for conservation, keeping or production. Lately, new species are being introduced in aquaculture, although for some of them the basic knowledge is still incomplete. Moreover, there are further issues connected to acclimatising the new species to artificial conditions and have them reproduce successfully. Studies on one of those new species, meagre (Argyrosomus regius), are still on early stages and females are usually the preferred test subjects. Reproduction in captivity, though, needs to be analysed also from the male point of view to have a complete image of the possible problems and solutions available to have a successful spawning. So far, meagre did not reproduce in captivity independently. One possible answer is the use of Gonadotropin release hormone agonist (GnHRa). In our experiment, the hormone was delivered to 4 males (8905 g ± 1146 g), during the reproductive season (5 May - 1 September 2015), through the application of subcutaneous implants containing 50 μg/kg of GnHRa every second week. To evaluate the effects of the implants during the reproductive season, milt was collected and four parameters were analysed: spermiation index, sperm density, sperm motility duration after activation and sperm survival at 4˚C. All parameters were evaluated twice per sample and a mean was obtained. Results show a reduction of the spermiation index (p: 0.066) and of the sperm density (p: 0.002) over the course of the experiment, while the sperm motility percentage and the sperm survival after activation do not appear to change (p>>0.05). The reduction of the milt concentration has been observed also in other species treated with this hormone. In fact, GnHRa is linked to the increase of the milt volume and the spermiation index. These results indicate that meagre males treated with GnHRa have a better chance to reproduce in captivity even if they are not well acclimatised to the environment. (Less)
Popular Abstract
Reproduction of hatchery-produced meagre (Argyrosomus regius) in captivity: effects of GnRHa implants on sperm quality

Aquaculture today is gaining importance in the fish management and production and can be a useful tool for sustainable production and conservation. Lately new species are being introduced, but for some of them basic knowledge is still incomplete. Moreover there are also issues connected to acclimatising those new species to captivity. Studies on one of those new species, meagre (Argyrosomus regius), are still on an early stage and, so far, females where the preferred test subjects. In this experiment, aimed at describing new ways to overcome problems related to failed reproduction in artificial environments in meagre,... (More)
Reproduction of hatchery-produced meagre (Argyrosomus regius) in captivity: effects of GnRHa implants on sperm quality

Aquaculture today is gaining importance in the fish management and production and can be a useful tool for sustainable production and conservation. Lately new species are being introduced, but for some of them basic knowledge is still incomplete. Moreover there are also issues connected to acclimatising those new species to captivity. Studies on one of those new species, meagre (Argyrosomus regius), are still on an early stage and, so far, females where the preferred test subjects. In this experiment, aimed at describing new ways to overcome problems related to failed reproduction in artificial environments in meagre, males were used to evaluate the effects of the Gonadotropin release hormone agonist (GnRHa). Results show that the hormone lowers milt density and spermiation index during the reproductive season, while sperm motility percentage and sperm survival after activation do not appear to change.

Meagre shows great potential for production, but there are some issues related to its reproduction in captivity. By using a subcutaneous implant, 4 males where delivered 50 μg/kg of GnRHa, in an attempt to boost sperm quality and production. This substance has been proven useful when used in other species presenting the same problem. The implants were inserted every two weeks and their effects were evaluated weekly using four variables: spermiation index, sperm density, sperm motility duration after activation and sperm survival at 4˚C.
After using linear regression to analyse the data collected, we found out that milt density decreased significantly during the reproductive season, as also seen in other species. Even though the effect of GnRHa is to increase milt volume, a spermiation index reduction was observed. Sperm motility duration after activation and survival at 4˚C where consistent during the experiment.

Our results are similar to those seen in other species treated similarly and make this work a valuable starting point for a larger effort put in meagre's production in captivity. In fact, since knowledge on meagre's ecology is still incomplete and there is a serious risk of wild stock crash in the Mediterranean region, the possibility of a reproduction in captivity can be a useful tool in the species' conservation. It can also be seen as a possible solution to overfishing and restocking, as well as a way to produce a high quality product still not exploited to its' full potential.

Supervisors:Mylonas C. Costantinos (HCMR, Crete), Anders Persson ( Aquatic Ecology department, Lund)
Master´s Degree Project 45 credits in Biology, 2015
Biology Department, Lund University (Less)
Please use this url to cite or link to this publication:
author
Biglino, Tommaso
supervisor
organization
course
BION01 20141
year
type
H2 - Master's Degree (Two Years)
subject
language
English
id
5434281
date added to LUP
2015-05-27 13:55:57
date last changed
2015-08-07 15:00:15
@misc{5434281,
  abstract     = {Aquaculture is a growing sector and many studies are carried out to select and optimize species for conservation, keeping or production. Lately, new species are being introduced in aquaculture, although for some of them the basic knowledge is still incomplete. Moreover, there are further issues connected to acclimatising the new species to artificial conditions and have them reproduce successfully. Studies on one of those new species, meagre (Argyrosomus regius), are still on early stages and females are usually the preferred test subjects. Reproduction in captivity, though, needs to be analysed also from the male point of view to have a complete image of the possible problems and solutions available to have a successful spawning. So far, meagre did not reproduce in captivity independently. One possible answer is the use of Gonadotropin release hormone agonist (GnHRa). In our experiment, the hormone was delivered to 4 males (8905 g ± 1146 g), during the reproductive season (5 May - 1 September 2015), through the application of subcutaneous implants containing 50 μg/kg of GnHRa every second week. To evaluate the effects of the implants during the reproductive season, milt was collected and four parameters were analysed: spermiation index, sperm density, sperm motility duration after activation and sperm survival at 4˚C. All parameters were evaluated twice per sample and a mean was obtained. Results show a reduction of the spermiation index (p: 0.066) and of the sperm density (p: 0.002) over the course of the experiment, while the sperm motility percentage and the sperm survival after activation do not appear to change (p>>0.05). The reduction of the milt concentration has been observed also in other species treated with this hormone. In fact, GnHRa is linked to the increase of the milt volume and the spermiation index. These results indicate that meagre males treated with GnHRa have a better chance to reproduce in captivity even if they are not well acclimatised to the environment.},
  author       = {Biglino, Tommaso},
  language     = {eng},
  note         = {Student Paper},
  title        = {Reproduction of hatchery-produced meagre (Argyrosomus regius) in captivity: effects of GnRHa implants on sperm quality},
  year         = {2015},
}