Toward the development of a rearing protocol for juvenile dusky kob, Argyrosomus japonicus (Pisces: Sciaenidae)
- Authors: Collett, Paul David
- Date: 2008
- Subjects: Argyrosomus -- South Africa , Mariculture -- South Africa , Fishes -- Nutrition -- South Africa , Fishes -- Growth -- South Africa , Fish trade -- South Africa , Sciaenidae
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5325 , http://hdl.handle.net/10962/d1005171 , Argyrosomus -- South Africa , Mariculture -- South Africa , Fishes -- Nutrition -- South Africa , Fishes -- Growth -- South Africa , Fish trade -- South Africa , Sciaenidae
- Description: The South African mariculture industry is developing the rearing technology of indigenous fish species. Dusky kob (Argyrosomus japonicus) has high-quality flesh and a good market demand. Research is needed to determine the environmental requirements under which growth of dusky kob is optimised. This study assessed the effect of temperature, light intensity, feeding frequency and stocking density, respectively, on growth, feed conversion ratio (FCR) and survival of juvenile dusky kob within a weight range of 10-60 g fish⁻¹) in a series of four growth trials. The effect of temperature on growth and FCR was assessed at 14 temperatures from 17 to 28°C. The temperature for best growth was estimated to be 25.3 °C, while 21.4 °C was the temperature at which the best FCR was achieved. A growth trial testing the effect of light intensity on growth showed that light intensity did not affect growth in the range of 23 – 315 lx. Fish fed a restricted ration of 3.6% body weight per day (chapter 2) or 3.41% body weight per day (chapter 4) had a better FCR than fish fed to satiation. A trial to assess the effect of feeding frequency on growth and FCR showed that fish fed both two or three times daily grew better than those fed once daily. FCR was best in fish that were fed once or twice daily. Preliminary analysis of the results from a stocking density trial showed that stocking density in the range of 10 – 50 kg m⁻³ did not affect growth of juvenile dusky kob. It is recommended to culture dusky kob at a temperature of 25.3 - 21.4 °C at stocking densities up 50 kg m⁻³ to maximise growth. However, a study is needed to determine the environmental conditions needed to maximise profit under commercial conditions. The results allow the South African industry the opportunity to assess the culture potential of this species. In addition, the results will help develop protocols that can be used in other South African candidate aquaculture species such as silver kob, yellowtail, white-stumpnose and sole.
- Full Text:
- Date Issued: 2008
- Authors: Collett, Paul David
- Date: 2008
- Subjects: Argyrosomus -- South Africa , Mariculture -- South Africa , Fishes -- Nutrition -- South Africa , Fishes -- Growth -- South Africa , Fish trade -- South Africa , Sciaenidae
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5325 , http://hdl.handle.net/10962/d1005171 , Argyrosomus -- South Africa , Mariculture -- South Africa , Fishes -- Nutrition -- South Africa , Fishes -- Growth -- South Africa , Fish trade -- South Africa , Sciaenidae
- Description: The South African mariculture industry is developing the rearing technology of indigenous fish species. Dusky kob (Argyrosomus japonicus) has high-quality flesh and a good market demand. Research is needed to determine the environmental requirements under which growth of dusky kob is optimised. This study assessed the effect of temperature, light intensity, feeding frequency and stocking density, respectively, on growth, feed conversion ratio (FCR) and survival of juvenile dusky kob within a weight range of 10-60 g fish⁻¹) in a series of four growth trials. The effect of temperature on growth and FCR was assessed at 14 temperatures from 17 to 28°C. The temperature for best growth was estimated to be 25.3 °C, while 21.4 °C was the temperature at which the best FCR was achieved. A growth trial testing the effect of light intensity on growth showed that light intensity did not affect growth in the range of 23 – 315 lx. Fish fed a restricted ration of 3.6% body weight per day (chapter 2) or 3.41% body weight per day (chapter 4) had a better FCR than fish fed to satiation. A trial to assess the effect of feeding frequency on growth and FCR showed that fish fed both two or three times daily grew better than those fed once daily. FCR was best in fish that were fed once or twice daily. Preliminary analysis of the results from a stocking density trial showed that stocking density in the range of 10 – 50 kg m⁻³ did not affect growth of juvenile dusky kob. It is recommended to culture dusky kob at a temperature of 25.3 - 21.4 °C at stocking densities up 50 kg m⁻³ to maximise growth. However, a study is needed to determine the environmental conditions needed to maximise profit under commercial conditions. The results allow the South African industry the opportunity to assess the culture potential of this species. In addition, the results will help develop protocols that can be used in other South African candidate aquaculture species such as silver kob, yellowtail, white-stumpnose and sole.
- Full Text:
- Date Issued: 2008
Dennett's compatibilism considered
- Authors: Puttergill, Julian Gatenby
- Date: 1997
- Subjects: Dennett, Daniel Clement , Intentionality (Philosophy)
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:2718 , http://hdl.handle.net/10962/d1002848 , Dennett, Daniel Clement , Intentionality (Philosophy)
- Description: My basic concern in this thesis is to examine the details behind Dennett's attempt to reconcile the notions of mechanism and responsibility. In the main this involves an examination of how he tries to secure a compatibilism between mechanistic and intentional explanations by developing a systematised conception of intentional explanation. I begin by briefly discussing the various notions needed for understanding what is at stake in the area and where the orthodoxy on the matter lies. As such the first three sections of the work are not focussed on Dennett's work itself and playa stage-setting role for the deeper work to follow. These notions include the likes of the rationale behind attributing moral responsibility, agency and action, mechanism and mechanistic explanation, and intentional explanation. I suggest that the basic intuition regarding mechanism and responsibility is such that the two are seen to be incompatible with each other. The main reason for this lies in an intuition that mechanism undermines intentional explanation and so renders the notion of action largely empty. Action, I show, is at the heart of our attribution of responsibility and is dependent on intentional explanation. Having presented these issues, I turn to the details of Dennett's 'intentional systems theory'. I argue that Dennett attempts to avoid the intuition that mechanism is incompatible with responsibility by developing a specialised account of intentional explanation. Dennett calls it the intentional stance. r highlight the two important features of this intentional stance, namely rationality and intentionality. r show that Dennett's position on rationality and intentionality is such that it does allow him to secure an explanatory compatibilism between mechanism and his sort of intentional explanation. I argue, however, that his sort of intentional explanation does not fulfil our requirements for ascribing agency or moral responsibility. This is accomplished in part by developing alternative conceptions of the two notions. Out of this I develop a different sort of intentional stance, which I call the folk stance. I show finaIly that Dennett's compatibilist move is incapable of being applied to the folkstance from which we do in fact make attributions of responsibility, and so conclude thatDennett fails to make the case for reconciling mechanism and responsibility.
- Full Text:
- Date Issued: 1997
- Authors: Puttergill, Julian Gatenby
- Date: 1997
- Subjects: Dennett, Daniel Clement , Intentionality (Philosophy)
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:2718 , http://hdl.handle.net/10962/d1002848 , Dennett, Daniel Clement , Intentionality (Philosophy)
- Description: My basic concern in this thesis is to examine the details behind Dennett's attempt to reconcile the notions of mechanism and responsibility. In the main this involves an examination of how he tries to secure a compatibilism between mechanistic and intentional explanations by developing a systematised conception of intentional explanation. I begin by briefly discussing the various notions needed for understanding what is at stake in the area and where the orthodoxy on the matter lies. As such the first three sections of the work are not focussed on Dennett's work itself and playa stage-setting role for the deeper work to follow. These notions include the likes of the rationale behind attributing moral responsibility, agency and action, mechanism and mechanistic explanation, and intentional explanation. I suggest that the basic intuition regarding mechanism and responsibility is such that the two are seen to be incompatible with each other. The main reason for this lies in an intuition that mechanism undermines intentional explanation and so renders the notion of action largely empty. Action, I show, is at the heart of our attribution of responsibility and is dependent on intentional explanation. Having presented these issues, I turn to the details of Dennett's 'intentional systems theory'. I argue that Dennett attempts to avoid the intuition that mechanism is incompatible with responsibility by developing a specialised account of intentional explanation. Dennett calls it the intentional stance. r highlight the two important features of this intentional stance, namely rationality and intentionality. r show that Dennett's position on rationality and intentionality is such that it does allow him to secure an explanatory compatibilism between mechanism and his sort of intentional explanation. I argue, however, that his sort of intentional explanation does not fulfil our requirements for ascribing agency or moral responsibility. This is accomplished in part by developing alternative conceptions of the two notions. Out of this I develop a different sort of intentional stance, which I call the folk stance. I show finaIly that Dennett's compatibilist move is incapable of being applied to the folkstance from which we do in fact make attributions of responsibility, and so conclude thatDennett fails to make the case for reconciling mechanism and responsibility.
- Full Text:
- Date Issued: 1997
- «
- ‹
- 1
- ›
- »