Fisheries and cage culture of three reservoirs in west Java, Indonesia; a case study of ambitious development and resulting interactions

The interactions between cage culture and wild fishery activities in three Indonesian reservoirs, Saguling, Cirata and Jatiluhur, of the greater Ciratum watershed, West Java, were evaluated using historical data and interviews with cage culture operators. In all three reservoirs, cage culture of common carp, Cyprinus carpio L., and later of common carp and Nile tilapia, Oreochromis niloticus (L.), were encouraged as an alternative livelihood for persons displaced by the impoundment. Currently, a two-net culture system, locally known as 'lapis dua', in which in the inner cage (7 × 7 × 3 m) is used for common carp culture and the outer cage (7 × 7 × 5/7 m) is stocked with Nile tilapia, is practised. On average each cage is stocked with  approximately 100 kg fingerlings each of common carp and Nile tilapia. The numbers of cages and production of cultured fish has increased in the reservoirs, but total and per cage production began to decline from about 1995 in Saguling from 2200 kg cage−1 in 1989 to <500 kg cage−1 in 2002, and in Cirata from a peak of approximately 2300 kg cage−1 in 1995 to approximately 400 kg cage−1 in 2002. In Jatiluhur, which has a considerably lower cage density, total fish production and production per cage has increased since 2000, and currently is approximately 4000 kg cage−1, close to production in the early years of cage culture activities. The cage culture operations also resulted in substantial nutrient loading, estimated at 3.2, 15.2 and 3.1 t of nitrogen and 134, 636 and 128 kg of phosphorous per year in the maximum years of production for Saguling, Cirata and Jatiluhur reservoirs, respectively. In later years, when cage culture production was high, fish kills occurred in the cages, and in Jatiluhur reservoir coincided with a dramatic decline in wild fishery catches. An attempt is made to determine the maximum number of cages for each of the reservoirs that will bring long-term sustainability of cage culture operations and the wild fisheries in the three reservoirs.

Effect of cage colour and light environment on the skin colour of Australian Snapper Pagrus auratus (Bloch & Schneider, 1801)

A two-factor experiment was performed to evaluate the effects of cage colour (black or white 0.5 m³ experiment cages) and light environment (natural sunlight or reduced level of natural sunlight) on the skin colour of darkened Australian snapper. Each treatment was replicated four times and each replicate cage was stocked with five snapper (mean weight=351 g). Snapper exposed to natural sunlight were held in experimental cages located in outdoor tanks. An approximately 70% reduction in natural sunlight (measured as PAR) was established by holding snapper in experimental cages that were housed inside a 'shade-house' enclosure. The skin colour of anaesthetized fish was measured at stocking and after a 2-, 7- and 14-day exposure using a digital chroma-meter (Minolta CR-10) that quantified skin colour according to the L*a*b* colour space. At the conclusion of the experiment, fish were killed in salt water ice slurry and post-mortem skin colour was quantified after 0.75, 6 and 22 h respectively. In addition to these trials, an ad hoc market appraisal of chilled snapper (mean weight=409 g) that had been held in either white or in black cages was conducted at two local fish markets. Irrespective of the sampling time, skin lightness (L*) was significantly affected by cage colour (P<0.05), with fish in white cages having much higher L* values (L*≈64) than fish held in black cages (L*≈49). However, the value of L* was not significantly affected by the light environment or the interaction between cage colour and the light environment. In general, the L* values of anaesthetized snapper were sustained post mortem, but there were linear reductions in the a* (red) and b* (yellow) skin colour values of chilled snapper over time. According to the commercial buyers interviewed, chilled snapper that had been reared for a short period of time in white cages could demand a premium of 10–50% above the prices paid for similar-sized snapper reared in black cages. Our results demonstrate that short-term use of white cages can reduce the dark skin colour of farmed snapper, potentially improving the profitability of snapper farming.

Influence of chromium content on the dry machining performance of cathodic arc evaporated TiA1N coatings

Physical vapour deposition (PVD) titanium aluminium nitride coated cutting tools are used extensively in global manufacturing for reducing production costs and improving productivity in a number of aggressive metal-cutting operations, namely, dry and high-speed machining. In this investigation, the performance of Ti1−xAlxN and Ti1−x−yAlxCryN coatings was assessed on Co-HSS twist drills used to machine grey cast iron. The failure criterion for drills was defined as a critical sized flank wear land at the outer corners of the drills. Using this criterion, the average tool life of uncoated twist drills was increased by factors of 2.5, 3.0 and 3.0 by Ti0.59Al0.41N, Ti0.27Al0.19Cr0.54N and Ti0.21Al0.14Cr0.65N coatings, respectively. Notwithstanding the similar increase in average tool life, the Ti1−x−yAlxCryN coatings produced more consistent results than the Ti1−xAlxN coated drills with standard deviations of 67, 3 and 19 holes, respectively. This result has significant practical implications in manufacturing, since drills are not replaced on an individual basis, but rather on a preset tool change frequency. The present paper discusses the performance of Ti1−xAlxN and Ti1−x−yAlxCryN coated drills in terms of average and practical drill life and concludes with remarks on the characterisation of PVD coatings and their significance on the performance of Co-HSS twist drills when dry machining grey cast iron.

Reducing the macroparticle content of cathodic arc evaporated TiN coatings

Cathodic arc evaporation (CAE) is a widely used technique for generating highly ionised plasma from which hard, wear-resistant PVD coatings can be deposited. A major drawback of this technique is the emission of micrometer-sized droplets of cathode material from the arc spot, which are commonly referred to as ‘macroparticles’. In this study, the effect of cathode poisoning was investigated as a method to reduce the number of macroparticles in PVD coatings. While the study focuses on the reduction of macroparticles in titanium nitride coatings, the outcomes and key findings can be broadly applied to the cathodic arc process, in particular, for the reduction of macroparticles in more advanced CAE coatings. The results support earlier findings that have shown that poisoning of the cathode can reduce the number of macroparticles emitted from the arc spot. The results of glow discharge optical emission spectroscopy (GD-OES) showed that the titanium content of the coatings varied little between the respective coatings despite changes in the deposition pressure from 0.1 to 1.2 Pa. The GD-OES results also showed the presence of oxide contamination at the surface of the coatings, which was significantly reduced with increasing deposition pressure. The coatings were also deposited onto high-speed steel twist drills to compare the metal-cutting performance when dry drilling a workpiece of cast iron. The results of the drill tests showed that tool life increased with a reduction in the number of macroparticles.

Effects of cage netting colour and density on the skin pigmentation and stress response of Australian snapper Pagrus auratus (Bloch & Schneider, 1801)

The unnaturally dark pigmentation of cultured Australian snapper Pagrus auratus can be improved through dietary astaxanthin supplementation and by holding fish in tanks with a white background. The practical application of these  laboratory-based findings was examined with two experiments to establish if the advantages of transferring fish to light coloured tanks before harvest could be achieved on-farm using white cages and to determine the effects of fish density on skin colour. For the first experiment, snapper (mean TL=29.7 cm) were transferred from a commercial snapper sea cage to black or white netted cages and fed diets supplemented with unesterified astaxanthin (supplied as Lucantin^® Pink, BASF) at 0 or 39 mg kg⁻¹ for 42 days. Skin colour was measured using the CIE L* (black–white), a* (green–red), b* (blue–yellow) colour scale. Snapper held in white netting cages became significantly lighter (higher L* ) than snapper held in black cages; however, values were not as high as previous laboratory-based studies in which snapper were held in white plastic-lined cages. Snapper fed astaxanthin displayed significantly greater a*and b* values, and total carotenoid concentrations after 42 days. In addition, total carotenoids were higher in fish from black than white cages. The second experiment was designed to investigate whether density reduced the improvements in skin colour achieved by holding fish in white coloured cages and whether cage colour affected stress. Snapper (mean weight=435 g) were acclimated to black cages and fed 39 mg kg⁻¹ astaxanthin for 44 days before transferring to black or white plastic-lined cages at 14 (low), 29 (mid) or 45 (high) kg m⁻³ for 7 days after which time skin colour, plasma cortisol and plasma glucose concentrations were measured. Skin lightness (L* ) was greater in snapper transferred to white plastic-lined cages with the lightest coloured fish obtained from the lowest density after 7 days. Density had no effect on plasma cortisol or glucose levels after 7 days, although plasma cortisol was elevated in snapper from black cages. For improved skin colouration we recommend feeding unesterified astaxanthin at 39 mg kg⁻¹ for approximately 6 weeks and transferring snapper to white plastic-lined cages or similar at low densities for short periods before harvest rather than producing fish in white netting sea cages subject to biofouling.

Cage colour and post-harvest K+ concentration affect skin colour of Australian snapper Pagrus auratus (Bloch & Schneider, 1801)

In an attempt to improve post-harvest skin colour in cultured Australian snapper Pagrus auratus, a two-factor experiment was carried out to investigate the effects of a short-term change in cage colour before harvest, followed by immersion in K⁺-enriched solutions of different concentrations. Snapper supplemented with 39 mg unesterified astaxanthin kg⁻¹ for 50 days were transferred to black (for 1 day) or white cages (for 1 or 7 days) before euthanasia by immersing fish in seawater ice slurries supplemented with 0, 150, 300, 450 or 600 mmol L⁻¹ K⁺ for 1 h. Each treatment was replicated with five snapper (mean weight=838 g) held individually within 0.2 m³ cages. L*, a* and b* skin colour values of all fish were measured after removal from K⁺ solutions at 0, 3, 6, 12, 24 and 48 h. After immersion in K⁺ solutions, fish were stored on ice. Both cage colour and K⁺ concentration significantly affected post-harvest skin colour (P<0.05), and there was no interaction between these factors at any of the measurement times (P>0.05). Conditioning dark-coloured snapper in white surroundings for 1 day was sufficient to significantly improve skin lightness (L*) after death. Although there was no difference between skin lightness values for fish held for either 1 or 7 days in white cages at measurement times up to 12 h, fish held in white cages for 7 days had significantly higher L* values (i.e. they were lighter) after 24 and 48 h of storage on ice than those held only in white cages for 1 day. K⁺ treatment also affected (improved) skin lightness post harvest although not until 24 and 48 h after removal of fish from solutions. Before this time, K⁺ treatment had no effect on skin lightness. Snapper killed by seawater ice slurry darkened (lower L*) markedly during the first 3 h of storage in contrast with all K⁺ treatments that prevented darkening. After 24 and 48 h of storage on ice, fish exposed to 450 and 600 mmol L⁻¹ K⁺ were significantly lighter than fish from seawater ice slurries. In addition, skin redness (a*) and yellowness (b*) were strongly dependent on K⁺ concentration. The initial decline in response to K⁺ was overcome by a return of a* and b* values with time, most likely instigated by a redispersal of erythrosomes in skin erythrophores. Fish killed with 0 mmol L⁻¹ K⁺ maintained the highest a* and b* values after death, but were associated with darker (lower L*) skin colouration. It is concluded that a combination of conditioning snapper in white surroundings for 1 day before harvest, followed by immersion in seawater ice slurries supplemented with 300–450 mmol L⁻¹ K⁺ improves skin pigmentation after >24 h of storage on ice.

Improved cathodic disbondment performance of polyethylene blends

Cathodic disbondment (CD) performance of a range of modified polyethylenes (PE) compression molded on to steel plates at 320[degrees]C is reported. Adhesion strength was measured by the 90[degrees] peel test and good dry adhesion strength was obtained for all modified polyethylene materials and blends, as well as for the neat polymer. It is shown that dry bond strength does not correlate with CD performance. Initial results of wet peel tests of samples in various concentrations of NaOH are presented where it is observed that for samples with improved wet adhesion strength, CD performance was also Improved. Surface polarity was determined from contact angle measurements, and it is shown that increased surface polarity of the coating was not the only determinant for improved CD performance. Inorganic fillers such as talc were also found to improve CD performance by changing the bulk properties, with little measurable change in polarity. Some mechanistic aspects of CD performance are also discussed.

Modification of thermoplastic coatings for improved cathodic disbondment performance on a steel substrate : a study on failure mechanisms

The effect of blending two different materials with a medium density polyethylene for use as pipe coatings is presented. The influence of such blending on properties such as cathodic disbondment (CD) and wet adhesion on steel is investigated. The components blended include a functionalised polyethylene (PE) containing the polar functionality, maleic anhydride (MAH) and an amorphous elastomer, ethylene-propylene-diene terpolymer (EPDM). It was found that modification of PE with small amount (2.5–3 wt%) of either blended MAH-g-PE or EPDM resulted in a significant improvement in CD performance and wet adhesion strength. The mode of failure and disbondment mechanism was investigated using energy dispersive X-ray spectroscopy (EDXS) and X-ray photoelectron spectroscopy (XPS). The greater resistance of migration of sodium ions increases with the incorporation of the modifiers, and it is proposed that this results in an increase in CD performance.