Suspension culture of the great scallop Pecten maximus in Galicia, NW Spain: intermediate secondary culture from juveniles to young adults.
ABSTRACT A strategy for producing juvenile Pecten pecten: see scallop. maximus to a suitable size for final culture ([approximately equal to] 20-60 mm shell-height) within a year is suggested. Effects of stocking density, fouling on cages and shells, and handling frequency (every 1, 2, or 3 mo) on scallop scallop or pecten, marine bivalve mollusk. Like its close relative the oyster, the scallop has no siphons, the mantle being completely open, but it differs from other mollusks in that both mantle edges have a row of steely blue "eyes" and growth and survival were investigated. Small juveniles (16.8 [+ or -] 3.0 mm) were initially stocked in August at densities of 24, 36, and 48 scallops [quarter.sup.-1] (17% to 34% coverage), and 35.5 [+ or -] 5.1 mm scallops were restocked in January to 6, 12, 18, and 24 [quarter.sup.-1] (18% to 73%). Survival was neither affected by stocking density nor handling, and was 98% the first period and from 93.2% to 96.9% between January and July. Shell-growth was mainly affected by stocking density and less affected by handling frequency. Growth slowed down during the winter months, and stocking density influenced growth during all seasons. Juveniles kept at the lowest densities obtained highest growth. Final mean shell-height was 54.8-67.2 mm and coverage 22% to 165%. Scallops handled monthly and bimonthly bi·month·ly
1. Happening every two months.
2. Happening twice a month; semimonthly.
1. Once every two months.
2. Twice a month; semimonthly.
n. pl. had significantly larger sizes than scallops handled every three months. Fouling on the cages increased with rising sea temperature, whereas high stocking density significantly reduced fouling on cages. Effective production during intermediate secondary culture in Galicia should include high initial stocking density in August, restocking to low density in January, and changes or cleaning of cages every second month.
KEY WORDS: scallop, Pecten maximus, intermediate suspension culture, stocking density, handling, fouling
The great scallop, Pecten maximus, is a commercially important species in Europe, and aquaculture aquaculture, the raising and harvesting of fresh- and saltwater plants and animals. The most economically important form of aquaculture is fish farming, an industry that accounts for an ever increasing share of world fisheries production. has been based on growth of spat spat
juvenile aquatic shellfish, especially oysters ready for settlement on solid surfaces—'spat fall'. coming either from hatchery hatchery
a commercial establishment dedicated to the hatching of bird eggs to provide day old chicks and poults to the poultry industry.
the contents of unfertilized eggs. Used in petfood manufacture. production or collection from the wild (Dao et al. 1999). In areas like western Norway and Atlantic Spain scallop culture depends on hatchery produced spat (Bergh & Strand Strand, street in London, England, roughly parallel with the Thames River, running from the Temple to Trafalgar Square. It is a street of law courts, hotels, theaters, and office buildings and is the main artery between the City and the West End.
1. 2001, Louro et al. 2005). The scallops are commonly grown intermediately in suspension culture before final grow-out by ear-hanging or in bottom culture to commercial size >100 mm. Intermediate culture comprises a primary stage from [approximately equal to] 3-20-mm shell height (Louro et al. 2005) and a secondary stage from [approximately equal to] 20-60 mm. From the secondary stage onwards on·ward
Moving or tending forward.
adv. also on·wards
In a direction or toward a position that is ahead in space or time; forward.
Adv. 1. the same techniques can be applied for spat obtained from hatchery production and from natural settlement on collectors (Roman et al. 2003).
Suspension culture of scallops may increase growth because of more favorable fa·vor·a·ble
1. Advantageous; helpful: favorable winds.
2. Encouraging; propitious: a favorable diagnosis.
3. temperature and food conditions than on the seabed (Wallace Wal·lace , Alfred Russel 1823-1913.
British naturalist who developed a concept of evolution that paralleled the work of Charles Darwin. & Reinsnes 1985, Dadswell & Parsons Parsons, city (1990 pop. 11,924), Labette co., SE Kans.; inc. 1871. It is a shipping point for dairy products, grain, and livestock. Manufactures include ammunition, wire and paper products, plastics, and appliances. 1992, Thorarinsdottir 1994, Lodeiros et al. 1998). Other factors related to culture technique and handling practice (i.e., stocking density, type of equipment, cleaning, grading, fouling, and predation predation
Form of food getting in which one animal, the predator, eats an animal of another species, the prey, immediately after killing it or, in some cases, while it is still alive. Most predators are generalists; they eat a variety of prey species. ) may have negative impact on scallop growth in suspension culture. Stocking density is one of the factors most often considered and many studies have shown an inverse relationship A inverse or negative relationship is a mathematical relationship in which one variable decreases as another increases. For example, there is an inverse relationship between education and unemployment — that is, as education increases, the rate of unemployment between growth and density (Widman & Rhodes 1991, Parsons & Dadswell 1992, Cote et al. 1993, Roman et al. 1999, Maguire & Burnell 2001, Roman et al. 2003). Although some authors have found that fouling does not affect scallop growth (Wallace & Reinsnes 1985, Widman & Rhodes 1991) and others suggest beneficial effects (Ross et al. 2002), fouling organisms Organisms
See also animals; bacteria; biology; plants; zoology.
Biology, Physiology. the synthesis in living organisms of more complex substances from simpler ones. Cf. catabolism. — anabolic, adj. are usually considered to limit growth, either by reducing water flow and food availability or by competing with the scallops for food (Paul & Davis 1986, Wildish et al. 1988, Cote et al. 1993, Claereboudt et al. 1994, Lodeiros & Himmelman 2000).
Removal of fouling organisms or changing the enclosures adds to operational costs in bivalve bivalve, aquatic mollusk of the class Pelecypoda ("hatchet-foot") or Bivalvia, with a laterally compressed body and a shell consisting of two valves, or movable pieces, hinged by an elastic ligament. aquaculture (Young-Lai & Aiken 1986, Taylor et al. 1997). Cleaning procedures are labor intensive Labor Intensive
A process or industry that requires large amounts of human effort to produce goods.
A good example is the hospitality industry (hotels, restaurants, etc), they are considered to be very people-oriented.
See also: Capital Intensive, Trading Dollars and may stress the scallops. The problem with fouling on the equipment is typically met by cleaning with high-pressure water or regular changes of nets or cages (Hardy 1991, Laing & Spencer 1997, Ross et al. 2002), whereas fouling on the shells may need to be removed by hand (Taylor et al. 1997). Frequent handling can affect growth and survival of P. maximus (Laing et al. 1999) and 23% mortality has been associated with repeated handling of Placopecten magellanicus during intermediate culture (Parsons & Dadswell 1992).
Previous suspension growth trials with P. maximus in O Grove O Grove (Galician) , Ogrobe (Galician alternative) or El Grueve (Spanish) is a municipality in Galicia, Spain, belonging to the province of Pontevedra.
[ edit ] Municipalities in Pontevedra
Cost-effective commercial production is a compromise between operational costs and husbandry husbandry
careful management of e.g. animals. Implies thrifty, humane, caring. See also animal husbandry. intensity. Therefore, knowledge of the interactions between stocking density, fouling, and cleaning frequency is important to optimize optimize - optimisation site-specific culture technique. Objectives of this paper were to study (1) the effect of stocking density on growth and survival of juveniles ([approximately equal to] 15-60 mm) from hatchery produced spat during the period from August to July; (2) the effect of fouling on cages and shells; and (3) the underlying effect of handling frequency. The work will contribute to a protocol describing the best husbandry practice during the intermediate secondary culture for great scallop in Galicia, Spain.
MATERIALS AND METHODS
The scallops were produced in the experimental hatchery of Centro Oceanografico de A Coruna (COAC COAC Commercial Operations Advisory Committee (US Customs)
COAC Collegi d'Arquitectes de Catalunya
COAC Combined Air and Space Operations Center (US Air Force) ) in Spain, by spawning adult P. maximus collected from the wild. Juvenile scallops were obtained after intermediate primary culture in sea-based nursery (Louro et al. 2005). Growth was in stacked Stacked is an American television sitcom that premiered on Fox on April 13, 2005. On May 18, 2006, Stacked was cancelled, leaving five episodes unaired in the United States. The last episode aired on January 11, 2006. rigid circular plastic cages (diameter 41.5 cm, height 8 mm, mesh Refers to an interconnect architecture that cross- connects several devices. See mesh network, wireless mesh network and switch fabric.
(character) mesh - The INTERCAL name for hash. size 10 mm) divided into 4 compartments In developmental biology, compartments are fields of cells of distinct cell lineage, cell affinity, and genetic identity. In a developing organ, all cells within a compartment possess similar affinities, and so intermingle with each other. (quarters), which secured an even distribution of scallops (Ill. in Roman et al. 2001). Each stack consisted of 8 cages where six held scallops, the top cage functioned as cover and the bottom cage was ballasted. The experiments took place in O Grove, Ria de Arousa, NW Spain, and the scallops were kept at 6-m depth in suspension culture from a commercial raft. Temperature, salinity sa·line
1. Of, relating to, or containing salt; salty.
2. Of or relating to chemical salts.
1. A salt of magnesium or of the alkalis, used in medicine as a cathartic.
2. , and chlorophyll a Noun 1. chlorophyll a - a blue-black plant pigment having a blue-green alcohol solution; found in all higher plants
chlorophyl, chlorophyll - any of a group of green pigments found in photosynthetic organisms; there are four naturally occurring forms were recorded weekly by the Centro de Control da Calidade do Medio Marino with a CTD CTD 1 Connective tissue disease, see there 2 Cumulative trauma disorder, see there (Fig. 1.).
[FIGURE 1 OMITTED]
The study was carried out between August 1, 2001 and July 9, 2002 and divided into two experiments because of increased scallop size. In both experiments the effect of stocking density and handling frequency were studied. Handling involved change of fouled cages with clean ones, monthly (H1), bimonthly (H2), and every three months (H3). At each handling time scallop shell-heights were measured with a caliper caliper
Instrument that consists of two adjustable legs or jaws for measuring the dimensions of material parts. Spring calipers have an adjusting screw and nut; firm-joint calipers use friction at the joint to hold the legs unmoving. to the nearest mm and the number of live scallops counted. Growth rate (mm [day.sup.-1]) was calculated on scallops handled monthly by the equation GR = ([h.sub.1] - [h.sub.0])/([t.sub.1] - [t.sub.0]), where [h.sub.1] and [t.sub.1] were the shell height and date at sampling, and [h.sub.0] and [t.sub.0] were the size and date of the previous sampling. Fouling on Cages was estimated occasionally after removal of scallops by subtracting the mean weight of a clean cage (581 [+ or -] 35 (sd) g, n = 25) from the wet weight of cages with fouling organisms. Fouling on the scallop shells scallop shell
vessel used for conferral of sacrament. [Christian Symbolism: Appleton, 88]
See : Baptism was removed by hand before wet weight measurement. The weight of settled organisms found on scallops in each quarter was pooled and expressed as g [quarter.sup.-1].
The experiment started August 1 with juveniles of mean shell height 16.8 [+ or -] 3.0 (sd) mm (n = 200) stocked at densities of 24, 36, and 48 scallops [quarter.sup.-1] (760-1500 scallops [m.sup.-2]), which covered 17% to 34% of the cage bottom area. Scallops were deployed in 6 stacks, each having two replicate rep·li·cate
1. To duplicate, copy, reproduce, or repeat.
2. To reproduce or make an exact copy or copies of genetic material, a cell, or an organism.
A repetition of an experiment or a procedure. cages regarding stocking density. Until October 3 the scallops were kept undisturbed un·dis·turbed
Not disturbed; calm.
1. quiet and peaceful: an undisturbed village
2. to acclimate in suspension culture because of high air and water temperatures. The scallops were transferred to clean cages and subsequent handling occurred on October 30 (H1), November 28 (H1 and H2), and finally on January 3 (H1 and H3). Two stacks of cages were sampled for each handling treatment, and fouling on cages was estimated for the HI and H3 groups. The experiment finished when the juvenile scallops had reached a mean size of [approximately equal to] 35-mm shell height.
On January 3 juveniles of mean shell height 35.5 [+ or -] 5.1 (sd) mm (n = 100) were stocked at densities of 6, 12, 18, and 24 scallops [quarter.sup.-1] (190-760 scallops [m.sup.-2]), which was equal to 18% to 73% coverage of the cage bottom area. Scallops were deployed in 6 stacks, each having two replicate cages with 6 and 12, one cage with 18 and one cage with 24 scallops [quarter.sup.-1]. The cages were randomly placed within stacks. Two stacks of cages were sampled at each handling date February 3 (H1), March 12 (H1 and H2), April 16 (H1 and H3), May 14 (H1 and H2), June 10 (H1), and July 9 (H1, H2 and H3). Fouling on cages was estimated at all sampling dates, whereas fouling settled on the scallop shells was weighed in April and July. The experiment ended when the scallops had reached a mean size of [approximately equal to] 60-mm shell height and were considered young adults.
The analyses were carried out by using the statistical package Statgraphics Plus 5. Shell height and calculated survival (%) at each sampling date were analyzed an·a·lyze
tr.v. an·a·lyzed, an·a·lyz·ing, an·a·lyz·es
1. To examine methodically by separating into parts and studying their interrelations.
2. Chemistry To make a chemical analysis of.
3. using one-way (monthly handling) and multifactor ANOVA anova
see analysis of variance.
ANOVA Analysis of variance, see there (remaining cases), factors being stocking density and handling frequency. Comparison between fouling weight on the cages was performed employing one-way ANOVA for each handling treatment. All survival data were arcsine [x.sup.0.5] transformed and Kolmogorov-Smirnov test In statistics, the Kolmogorov–Smirnov test (often called the K-S test) is used to determine whether two underlying one-dimensional probability distributions differ, or whether an underlying probability distribution differs from a hypothesized distribution, in either for normality normality, in chemistry: see concentration. and Bartlett test for homogeneity Homogeneity
The degree to which items are similar. of variances performed prior to analysis. Student-Newman-Keuls test (SNK SNK Shin Nihon Kikaku (Japanese: New Japan Product; video game manufacturer)
SNK Strong Name Key (.Net file extension)
SNK Shin Nihon Kikaku Corporation (Japan) ) test was used for posthoc comparisons. When necessary, natural log transformations were used. For comparison of fouling on the shells a multifactor ANOVA was designed, factors being handling frequency and stocking density. In most of the cases values did not follow the requirements of either normality or homogeneity of variances, and non-parametric Kruskal-Wallis tests were performed.
The highest temperatures were recorded during summer and autumn 2001, with values ranging between 14.0[degrees]C and 18.6[degrees]C. A sharp decrease was observed from November 5 down to a minimum of 9.0[degrees]C reached December 26. From January to July 2002 the temperature increase was slow but constant from 12.0[degrees]C to 15.7[degrees]C (Fig. 1). Salinity generally ranged between 35.0 and 35.5 psu except for occasional drops to 33.3 psu (Fig. 1). Chlorophyll a concentrations ranged from 0.5-1.0 [micro]g [L.sup.-1] from July to October 2001, whereas lower values (<0.5 [micro]g [L.sup.-1]) were recorded between November 2001 and March 2002. From spring to summer 2002 the concentration oscillated and showed several peaks between from 1.2-2.7 [micro]g [l.sup.-1] (Fig. 1).
Survival and Growth
Survival after two months (August 1 to October 3) in suspension culture was between 98.0% and 99.1%. No significant differences in survival were recorded throughout the experimental period, neither between scallops initially stocked at different densities or between groups handled at different frequencies. The pooled survival was 98.4 [+ or -] 2.6% at first sampling and 98.2 [+ or -] 3.6% at the end of the experiment (January 3).
Handling did not significantly affect shell-height growth in this experiment (Table 1), but significant differences related to stocking density (P = 0.017) appeared as soon as October 30 (Fig. 2). At this date scallops stocked at the lowest density, 24 [quarter.sup.-1], were significantly larger (31.4 [+ or -] 4.6 mm, n = 196) than scallops grown at 48 quarter 1 (29.7 [+ or -] 5.1 mm, n = 370). At November 28 the scallops stocked at 24 [quarter.sup.-1] were larger (36.2 mm [+ or -] 4.9, n = 191) than scallops stocked at both 36 (34.5 [+ or -] 4.9 mm, n = 192) and 48 (34.0 [+ or -] 4.8 mm, n = 192) [quarter.sup.-1] (Table 1). The growth rates Growth Rates
The compounded annualized rate of growth of a company's revenues, earnings, dividends, or other figures.
Remember, historically high growth rates don't always mean a high rate of growth looking into the future. were 0.163, 0.148, and 0.142 mm [day.sup.-1]. Even if slower growth rates (0.039, 0.025, and 0.017 mm [day.sup.-1]) were observed for all groups from November 28 to January 3 (Fig. 2), the final shell height differed significantly between all stocking densities, showing 37.6 [+ or -] 5.1 mm (n = 378), 35.2 [+ or -] 4.5 mm (n = 384) and 34.3 [+ or -] 4.9 mm (n = 384) for scallops held at 24, 36, and 48 [quarter.sup.-1], respectively (Fig. 2, Table 1).
[FIGURE 2 OMITTED]
Coverage of the cage bottom area had increased from 17% to 34% to 43% to 78% after 2 mo growth, and was 79% to 131% by January when the experiment ended. Growth rates varied with season and showed decreasing trends (fitted to power functions) with increased coverage percentage (Fig. 3a).
[FIGURE 3 OMITTED]
Fouling on Cages and the Shells
The weight of fouling organisms on cages was determined from October 30 for the H1 and H3 treatments. Monthly handling resulted in low accumulation (mean wet weight) of fouling organisms on the cages, with the highest build-up build·up also build-up
1. The act or process of amassing or increasing: a military buildup; a buildup of tension during the strike.
2. in October (94 [+ or -] 24.59 g) (Fig. 4). In November fouling on cages ranged from 18-41 g and in January from 29-101 g. Fouling was about five times higher (513.0 [+ or -] 89.5 g) on cages that had been in the sea for three months before handling (Fig. 4). Scallop shells were sparsely sparse
adj. spars·er, spars·est
Occurring, growing, or settled at widely spaced intervals; not thick or dense.
[Latin sparsus, past participle of spargere, to scatter. fouled with small specimens of the sponges Sycon sp and Leucosolenia sp.
[FIGURE 4 OMITTED]
Survival and Growth
No significant differences in survival were found neither related to stocking density nor to handling frequency during the six months of experimental time. Final survival ranged from 93.2% to 96.9% and final mean shell-height from 54.8 mm to 67.2 mm. Shell-growth was mainly affected by stocking density and less affected by handling frequency (Table 2). Scallops handled monthly (H1) did not differ significantly in size after one month (P = 0.05), but after 5 mo significant mean shell heights (P = 0.000) were shown between all stocking densities, showing 62.8, 59.3, 55.5, and 53.3 mm for scallops held at 6, 12, 18, and 24 [quarter.sup.-1], respectively (Fig. 5). The multifactor ANOVA showed similar growth for the two highest densities until May 14, whereas in July all densities showed significant different sizes (Table 2).
[FIGURE 5 OMITTED]
At the end of the experiment, shell height also showed an inverse relationship with stocking density within all handling treatments (Fig. 5). Scallops handled monthly (H1) and bimonthly (H2) did not differ in size at any of the sampling dates, but they were always significantly larger than scallops handled every three months (H3) (Table 2). The slowest growth occurred during January and February, whereas the highest growth rates were recorded from March to June. Reduced growth rates were again shown between June and July mainly at the higher stocking densities (Table 3).
Coverage of the cage bottom area increased from 18% to 73% to 22% to 165% during the experimental period (Fig. 3b). Growth rates showed a steeper decrease with increased coverage percentage than in experiment 1. The trend lines fitted to power functions, except for in June where it fitted a second order polynomial polynomial, mathematical expression which is a finite sum, each term being a constant times a product of one or more variables raised to powers. With only one variable the general form of a polynomial is a0xn+a function (Fig. 3b).
Fouling on Cages
The mean wet weight of fouling organisms on cages, handled monthly (H1), ranged between 19.8 [+ or -] 13.4 and 97.6 [+ or -] 43.5 g (Fig. 6). A slight increase was observed in the summer months. A significant higher amount of fouling organisms accumulated ac·cu·mu·late
v. ac·cu·mu·lat·ed, ac·cu·mu·lat·ing, ac·cu·mu·lates
To gather or pile up; amass. See Synonyms at gather.
To mount up; increase. on cages kept for two months in the sea (H2), with mean weights ranging from 161.4 [+ or -] 33.7 387.7 [+ or -] 72.5 g (Fig. 6). A significant increase in weight was observed from winter to summer (March < May < July, P = 0.000). The most fouling was on cages changed every 3 mo (H3), where the mean value in April, 469.9 [+ or -] 137.2 g, was significantly lower than the weight 654.6 [+ or -] 202.3 g recorded in July (Fig. 6).
[FIGURE 6 OMITTED]
Fouling on the Shells
The overall mean weight of fouling organisms found on scallop shells was 170.7 [+ or -] 155.4 g [quarter.sup.-1] (n = 110), but in April (322.7 [+ or -] 114.5 g [quarter.sup.1], n = 46) the weight was significantly higher (Kruskal-Wallis test, P = 0.0000) than in July (61.4 [+ or -] 58.5 g [quarter.sup.-1], n = 64) (Fig. 6). Handling frequency did not affect the settlement of fouling organisms on the shells in April (Kruskal-Wallis test, P = 0.4486), whereas in July significant lower amounts (one-way ANOVA, P = 0.0014) were found on shells handled every 3 mo (H3) than on shells handled more frequently (H1 and H2). The weights were 87.9 [+ or -] 82.8, 71.4 [+ or -] 54.2, and 33.8 [+ or -] 23.7 g [quarter.sup.-1] for the H1 (n = 16), H2 (n = 24), and H3 (n = 24) groups, respectively.
Stocking density affected fouling on the shells significantly in April (Kruskal-Wallis test, P = 0.0000) and in July (Kruskal-Wallis test, P = 0.0003) (Fig. 7). In April fouling was higher at 6 [quarter.sup.-1] (442.4 [+ or -] 81.6 g, n = 14) than at 12 [quarter.sup.-1] (330.6 [+ or -] 78.2 g, n = 16), which in turn was higher than 18 [quarter.sup.1] (222.0 [+ or -] 11.8 g, n = 8), whereas 18 and 24 [quarter.sup.-1] (198.2 [+ or -] 21.6 g, n = 8) not differed significantly. In July fouling at 6 [quarter.sup.1] (107.6 [+ or -] 80.9 g, n = 20) was higher than the other densities, 12 [quarter.sup.-1] (51.7 [+ or -] 32.4 g, n = 20), 18 [quarter.sup.-1] (37.3 [+ or -] 15.2 g, n = 12), and 24 [quarter.sup.1] (24.8 [+ or -] 8.4 g, n = 12). Frequent handling affected fouling at the two lowest stocking densities more than the two higher densities. Within each handling group the fouling showed a decreasing trend with increased density, and the lowest density always had more fouling than the others (Fig. 7). In April H1 scallops kept at 6 and 12 [quarter.sup.-1] were affected by handling and had significant more fouling than scallops at the higher densities. In July scallops kept at 6 [quarter.sup.-1] showed a significant relationship with handling frequency (H1 > H2 > H3), whereas handling had no significant effect on fouling at the other stocking densities.
[FIGURE 7 OMITTED]
This study showed that juvenile P. maximus had high survival and continuous growth during intermediate secondary culture in Galician waters from August 2001 to July 2002. Deployment of scallops of [approximately equal to] 16 and [approximately equal to] 35-mm shell height showed survival >98% and >93%, respectively, which were similar to results obtained for small (>4 mm, Louro et al. 2005) and larger (>26 mm, Roman et al. 2003) spat grown at the same site. The high survival indicated suitable environmental conditions, low predator predator
an animal that derives its life support by predation. impact, and acceptable husbandry practice; though stocking density and handling frequency influenced on growth.
Effect of Stocking Density on Growth
Stocking density was the main factor affecting growth as previously reported for juvenile P. maximus in suspension culture (Cano et al. 2000, Maguire & Burnell 2001, Roman et al. 2003, Louro et al. 2005). Consequently, juveniles kept at the lowest densities, 760 [m.sup.-2] (16-mm shell height) and 190 [m.sup.-2] (35-mm shell height), obtained the highest growth rates and final size. Seasonal impact on growth is shown for tropical (Lodeiros & Himmelman 2000) and temperate temperate /tem·per·ate/ (tem´per-at) restrained; characterized by moderation; as a temperate bacteriophage, which infects but does not lyse its host.
adj. (Maguire & Burnell 2001) scallops, and was also the case in our study. Stocking density influenced growth during all seasons. The scallops grew continuously but slower during the winter months, suggesting growth at higher densities may be feasible at colder temperatures (<15[degrees]C). This assumption was supported by our results where scallops kept at the two highest densities had similar shell-height before December (1,150 and 1,500 [m.sup.-2]) and after restocking the following year, between January and May (570 and 760 [m.sup.-2]). Growth rates <0.1-mm per day were only observed from December to February, but reducing stocking density could double the growth rate. The effect of stocking density was most pronounced in spring and summer, when conditions for growth were more favorable because of increased temperature and chlorophyll a. In spring coverage above 100% still gave good growth, but the highest growth rates were observed at coverage below 50%. This agrees with earlier observations of low coverage ([less than or equal to] 30%) facilitating better growth in P. maximus cultures (Maguire & Burnell 2001, Roman et al. 2003, Louro et al. 2005).
Fouling on Cages and Scallop Shells
Culture method, site, placement in the water column, current speed, and season are among factors that affect fouling (Claereboudt et al. 1994, Ross et al. 2002). Fouling on the cages increased with rising sea temperature, whereas high stocking density significantly reduced fouling on cages. We observed some species-specific colonizing patterns, which could have affected the environmental conditions inside the cages. The solitary solitary /sol·i·tary/ (sol´i-tar?e)
1. alone; separated from others.
2. living alone or in pairs only.
being the only one or ones. tunicate tunicate (t`nəkĭt), marine animal of the phylum Chordata, which also includes the vertebrates. Ciona intestinalis Ciona intestinalis is a Urochordata (sea squirt) whose genome has been sequenced and which has become, over the past decade, a major experimental model for developmental biologists. Four subspecies have been described. , a common nuisance COMMON NUISANCE. One which affects the public in general, and not merely some particular person. 1 Hawk. P. C. 197. See Nuisance. in bivalve cultures (Uribe et al. 2001, Carver carver /car·ver/ (kahr´ver) a tool for producing anatomic form in artificial teeth and dental restorations.
carver (carving instrument),
n et al. 2003, Ross et al. 2004), settled mainly underneath the cages. Colonial tunicates (i.e., Didemnum candidum, Diplosoma listerianum, Botryllus schlosseri The "Golden Star Tunicate" Botryllus schlosseri is an invasive, colonial ascidian tunicate that grows on slow-moving, submerged objects, plants, and animals in nearshore saltwater environments. , Botrilloides leachi, Dendrodoa grossularia, and Polyclinidae), which often covered the cage mesh completely may have caused major reduction in water flow and food availability. Other solitary tunicates, Phallusia mamillata, Ascidia spp, Ascidiella spp, Molgula spp, and the introduced species Styela clava The Stalked Sea Squirt, Styela clava, is a solitary, hermaphroditic, ascidian tunicate that is found off Australia and New Zealand, both coasts of North America, and Europe. settled inside and outside the cages. They also settled on scallop shells, mainly on the left, flat shell.
In our study the colonization colonization, extension of political and economic control over an area by a state whose nationals have occupied the area and usually possess organizational or technological superiority over the native population. of colonial and solitary tunicates and Porifera on the scallop shells might have prevented settlement of mussels and barnacles, which is a great problem in ear hanging cultures in southern Spain (Cano et al. 2000). Culture on the seabed produces P. maximus shells with little fouling (Minchin 2003) compared with long-term suspension culture in the upper level of the water column, which enhance fouling (Claereboudt et al. 1994). P. maximus in Galicia are often associated with more fouling organisms than the scallop Aequipecten opercularis when cultured in the same location (Roman, pers. comm.). A similar difference in resistance to fouling, related to natural habitat, has also been suggested between the species Euvola ziczac (recessed re·cess
a. A temporary cessation of the customary activities of an engagement, occupation, or pursuit.
b. The period of such cessation. See Synonyms at pause.
2. ) and Lyropecten nodosus (epifaunal) (Lodeiros et al. 1998).
Effect of Foaling foaling
parturition in the mare.
bringing on the birth of the foal, usually via the injection of oxytocin. and Handling Frequency on Growth
Less handling increased fouling on the cages, whereas fouling on shells was highest for scallops handled frequently. Similar, scallop growth was negatively affected in heavy fouled cages handled less frequently. Most likely the fouling on cages reduced the flow and food availability inside the cages and inhibited in·hib·it
tr.v. in·hib·it·ed, in·hib·it·ing, in·hib·its
1. To hold back; restrain. See Synonyms at restrain.
2. To prohibit; forbid.
3. growth of the scallops and fouling organisms on the shells. To counteract the effect of flow reduction the use of biological control organisms may be a solution to remove fouling on equipment and scallop shells (Ross et al. 2004). Fouling on the shells was, however, considered of minor importance to growth compared with the effect of stocking density in our study.
It may take some time before accumulated fouling on equipment affect scallop growth. A major difference in settlement of fouling organisms was demonstrated between pearl-nets that had been deployed for 2 and 16 wk in the Irish Sea Irish Sea, arm of the Atlantic Ocean, c.40,000 sq mi (103,600 sq km), 130 mi (209 km) long and up to c.140 mi (230 km) wide, lying between Ireland and Great Britain. It is connected with the Atlantic by the North Channel and (on the south) by St. George's Channel. (Ross et al. 2002). Grecian et al. (2000) showed that fouling influencing growth of Placopecten magellanicus varied by season and gear type. We did not see any effect of fouling on the cages after 2 mo, when mean wet-weight of the fouling ranged between 0.06 and 0.15 g [cm.sup.-2]. After 3 mo, however, when fouling ranged from 0.19-0.26 g [cm.sup.-2], scallop growth was reduced. Moya (1998) found that the growth rate of Argopecten purpuratus, cultured in pearl-nets in Chile, was affected already after 2 mo, when fouling on the pearl-nets was 0.12 g [cm.sup.-2]. Likewise, fouling on pearl nets strongly affected E. ziczac growth (Lodeiros & Himmelman 1996) and muscle and soft tissue yield of P. magellanicus (Claereboudt et al. 1994). The lower final shell height observed in experiment 2 for scallops kept undisturbed in the sea for three months could be explained by heavier fouling on cages, but because no growth differences were found in experiment 1, despite a considerable difference in fouling on cages, we considered fouling on cages of little importance during the winter.
Scallops handled monthly and bimonthly grew faster during spring and summer than scallops handled every three months. Despite the fact that scallops handled every three months were less disturbed, growth was most probably reduced because of heavier fouling on cages. Our growth results agree with Pit & Southgate (2003) who found that less frequent disturbance DISTURBANCE, torts. A wrong done to an incorporeal hereditament, by hindering or disquieting the owner in the enjoyment of it. Finch. L. 187; 3 Bl. Com. 235; 1 Swift's Dig. 522; Com. Dig. Action upon the case for a disturbance, Pleader, 3 I 6; 1 Serg. & Rawle, 298. (every 16 wk) affected shell growth of Pinctada margaritifera negatively. They found the lowest survival in trays cleaned every 4 wk, whereas we did not find any differences in survival regarding our handling regimen regimen /reg·i·men/ (rej´i-men) a strictly regulated scheme of diet, exercise, or other activity designed to achieve certain ends.
1. . In accordance Accordance is Bible Study Software for Macintosh developed by OakTree Software, Inc.
As well as a standalone program, it is the base software packaged by Zondervan in their Bible Study suites for Macintosh. with the work of Taylor et al. (1997) on Pinctada maxima, we found that fouling did not affect survival of 1-y-old P. maximus. Handling did not affect growth during autumn and winter months when the chlorophyll a content in the sea was the lowest. This contrast the results of Laing et al. (1999) who found that growth was reduced by frequent handling during winter-spring months with little food naturally available. They suggested increased level of stress in scallops disturbed monthly compared with bimonthly and every three months.
This study intended to produce information on the longest interval between cleaning that would provide best growth at the lowest labor costs. Scallops in cage culture will routinely be exposed to handling, and the present study considered handling stress associated with changing cages. In long-term suspension culture thinning of animals will be necessary, dirty cages must be replaced periodically by clean ones, inspection of cages for removal of predators can be advisable ad·vis·a·ble
Worthy of being recommended or suggested; prudent.
ad·visa·bil , and growth and survival should be surveyed at regular intervals. In our study no growth differences were found between scallops handled monthly and bimonthly. Thus, we suggest replacing fouled cages with clean ones every second month in spring-summer and every three months in autumn-winter when fouling is a lesser problem.
Experimental sampling as measurement, counting, and removal of fouling from the scallop shell was carried out simultaneously as relaying onto clean trays. Thus, possible stress related to disturbance and air exposure was limited and comparable to industrial husbandry procedures. Scallops are known to be sensitive animals, but juvenile P. maximus has been shown to withstand short-term emersion e·mer·sion
The act of emerging; emergence.
[From Latin mersus, past participle of (Christophersen 2000, Maguire et al. 1999), and therefore should not be seriously affected by the air exposure during sampling or transfer to clean cages.
When comparing with culturing smaller spat in intermediate primary stage (Louro et al. 2005), less management is required in the secondary stage. The larger cage mesh size used during secondary culture delays the time before silting, and clogging affects water flow and thus growth. The presence of predators must, however, be controlled, but this was considered manageable during secondary culture. Frequent handling involved removing small predators from cages, which prevented them from growing to a size potentially harmful to the scallops. Settlement of larvae Larvae, in Roman religion
Larvae: see lemures. from the most potential predators was low by end of summer when the secondary culture started, but peaked in spring and early summer. At that time the scallops had reached at least 50-mm shell height, a size too large to be predated on (Grefsrud 2006).
Removing fouling organisms and changing cages are time consuming and adds to operational costs. The present study revealed that no advantage regarding growth and survival was obtained by monthly compared with bimonthly handling, even during summer months. Thus, effective production during intermediate secondary culture in Galicia can be obtained by handling maximum every second month. A further saving can be achieved by operating with higher densities during periods of slower growth (i.e., winter conditions). In the period September to February coverage above 100% had little influence on scallop growth, but the rest of the year growth was maximized at low stocking densities. We therefore propose a strategy where spat are initially stocked at high density (48 [quarter.sup.-1]) in August, transferred to clean cages in October and restocked to 12 [quarter.sup.-1] in clean cages in January. With a procedure of cleaning or changing cages every second month after that, scallops are expected to reach suitable size for final culture (>60 mm shell height) in July of the same year.
The authors thank Recursos Marinos Grovenses (REMAGRO) for the participation and use of facilities, the crew of the ship REMAGRO II, and Juan Fernandez-Feijoo and Carmen Carmen
throws over lover for another. [Fr. Lit.: Carmen; Fr. Opera: Bizet, Carmen, Westerman, 189–190]
See : Faithlessness
the cards repeatedly spell her death. [Fr. Vazquez-Vazquez for valuable assistance. This study was financed by EU, project SCALQUAL contract no Q5CR 2000-70310. The CTD data were provided by the Centro de Control da Calidade do Medio Marino da Conselleria de Pesca da Xunta de Galicia The Xunta de Galicia is the political bureaucracy for the autonomous community of Galicia in Spain. According to the Galician Statute of Autonomy, it consists of the president, the vice-president (if necessary), and the specialized ministers (Conselleiros). .
LITERATURE CITED CITED Copyright in Transmitted Electronic Documents
CITEd Center for Implementing Technology in Education
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TABLE 1. Result of multifactor ANOVA and Student-Newman-Keuls (SNK) test showing effects of stocking density (24, 36, and 48 scallops per quarter), and handling frequency (H1, H2, and H3) on shell-height growth of juvenile great scallops in Experiment 1. Source of Variation Df F Ratio P Value November 28, 2000 Stocking density (SD) 2 10.08 0.0003 Handling (H) 1 1.02 0.3180 Interaction SD x H 2 0.03 0.9712 January 3, 2001 Stocking density (SD) 2 40.08 0.0000 Handling (H) 1 0.27 0.6040 Interaction SD x H 2 0.35 0.7040 Source of Variation Results of SNK Test November 28, 2000 Stocking density (SD) 48/q = 36/q < 24/q Handling (H) Interaction SD x H January 3, 2001 Stocking density (SD) 48/q < 36/q < 24/q Handling (H) Interaction SD x H TABLE 2. Result of multifactor ANOVA and Student-Newman-Keuls (SNK) test showing effects of stocking density and handling frequency (H1, H2, H3) on shell-height growth of juvenile great scallops in 2002. Mean shell-height (mm) at each stocking density, expressed as number of scallops per quarter (#/q), are shown in brackets. Multifactor ANOVA Date Main Effects SS DF MS F-Ratio March 12 A: handling 1.8408 1 1.8408 2.76 B: density 51.0021 3 17.0007 25.51 Interact AB 0.0788 3 0.0263 0.04 April 16 A: handling 30.0833 1 30.0833 40.43 B: density 94.6408 3 31.5469 42.4 Interact AB 0.0775 3 0.0258 0.03 May 14 A: handling 0.1633 1 0.1633 0.07 B: density 175.703 3 58.5675 24.87 Interact AB 0.3375 3 0.1125 0.05 July 09 A: handling 42.9356 2 21.4679 21.23 B: density 544.997 3 181.66 180.52 Interact AB 4.8228 6 0.8038 0.8 Multifactor ANOVA Date Main Effects p-Value Results of SNK Test March 12 A: handling 0.1160 H1 = H2 B: density 0.0000 6/q (44.4) > 12/q (42.4) > 18/q Interact AB 0.9892 (41.1) = 24/q (40.6) April 16 A: handling 0.0000 H1 (49.1) > H3 (46.7) B: density 0.0000 6/q (50.9) > 12/q (48.5) > 18/q Interact AB 0.9910 (46.6) = 24/q (45.6) May 14 A: handling 0.7957 H1 = H2 B: density 0.0000 6/q (57.2) > 12/q (53.5) > 18/q Interact AB 0.9857 (51.2) = 24/q (50.2) July 09 A: handling 0.0000 H1 (61.2) = H2 (60.5) > H3 B: density 0.0000 (58.4) Interact AB 0.5804 6/q (65.8) > 12/q (61.5) > 18/q (57.2) > 24/q (55.6) TABLE 3. Shell-height growth rates (mm day') of juvenile great scallops in 2002 grown at different stocking densities, expressed as number of scallops per quarter (#/q), and handled monthly (H1), bimonthly (H2) and every three months (H3). Handling Frequency Date Density 6/q 12/q 18/q 24/q H1 February 13 0.098 0.085 0.063 0.059 March 12 0.194 0.137 0.121 0.108 April 16 0.209 0.199 0.182 0.173 May 14 0.190 0.144 0.120 0.114 June 10 0.199 0.208 0.163 0.118 July 09 0.152 0.127 0.094 0.105 H2 March 12 0.125 0.096 0.079 0.070 May 14 0.206 0.180 0.163 0.159 July 09 0.169 0.159 0.116 0.095 H3 April 16 0.138 0.116 0.097 0.086 July 09 0.168 0.142 0.123 0.125
ANGELES LOURO, (1) GYDA CHRISTOPHERSEN, (2) THOROLF MAGNESEN (2) AND GUILLERMO ROMAN (1) *
(1) Instituto Espanol de Oceanografia, Centro Oceanografico de A Coruna, Spain; (2) Department of Biology. University of Bergen, Norway
* Corresponding author. E-mail: firstname.lastname@example.org