) on fragmented rhodoliths. The strong cueing to live coralline surfaces may have resulted from live coralline algal surfaces or surface biofilms. Growth, presented as post-settlement size, was significantly greater in scallops that settled onto whole vs. fragmented rhodolith substrates for both live (246.6 ± 1.9 vs. 238.9 ± 4.4 µm) and dead (244.2 ± 2.8 vs. 234.7 ± 5.6 µm) coralline surfaces. The structural and coralline cues provided by live, intact rhodoliths and their large-grained sediments contribute to the importance of rhodolith beds as nursery habitats by increasing both scallop settlement and postsettlement growth. Protection of living rhodolith habitats can enhance scallop and other invertebrate populations as well as the sustainability of scallop fisheries by enhancing early life stages.KEY WORDS: Argopecten ventricosus · Coralline · Rhodolith · Scallop · Larval settlement cues · Lithophyllum margaritae · Maerl · Bahía Concepción Resale or republication not permitted without written consent of the publisherMar Ecol Prog Ser 396: [49][50][51][52][53][54][55][56][57][58][59][60] 2009 nell 1985, Raimondi 1990), and thereby strongly influence population and community-level processes (Rodriguez et al. 1993, Connolly & Roughgarden 1999. While hydrodynamic processes are known to strongly influence the delivery of larvae to suitable substrates (Butman et al. 1988, Abelson & Denny 1997, behavior in response to cues is also important in determining settlement patterns (Crisp 1974, Hadfield 1986, Raimondi & Morse 2000.Settlement cues, often required for metamorphosis of marine invertebrate larvae (Morse & Morse 1984, Pearce & Scheibling 1990, are thought to be indicative of environmental features that enhance survivorship (e.g. habitat, refuge, food or conspecifics). Physical cues include hydrodynamics (Crisp 1955), light (Crisp & Ritz 1973), depth (Knight-Jones & Morgan 1966), surface structural complexity (Harvey et al. 1993, disturbance events (Woodin et al. 1995) and surface chemistry (Hay 1996, Steinberg & de Nys 2002. Biological cues include presence of conspecifics (Keough 1998) and bacterial or bioorganic films (Maki et al. 1989, Keough & Raimondi 1995, Huggett et al. 2006). In addition, physical and biological cues can act synergistically (Crisp & Meadows 1963, Gee 1965, Le Tourneux & Bourget 1988. Few studies have been conducted in the field to understand in situ larval responses (Keough & Raimondi 1995) and how the distribution or magnitude of various cues might influence larval settlement (Underwood & Keough 2000).Complex seaweed surfaces, such as those found in coralline algae, provide combinations of physical and biological cues that can influence settlement in a range of invertebrates (Walters et al. 1996, Steinberg & de Nys 2002. Species of geniculate and non-geniculate (crustose) forms of coralline red algae occur in most coastal environments (Bosence 1983). A variety of invertebrate larvae are induced to settle on coralline algae by the physical features of the complex surfaces found on att...

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Starting in 1997, mortality outbreaks in cultured oysters Crassostrea gigas have been reported in northwestern México. Previous studies have shown that massive die‐offs result from multi‐factor processes related to reproduction of the species. We studied the reproductive cycle and the condition index of cultured oysters in the coastal lagoon of El Soldado, Sonora, as well as the relationship of the life cycle with environmental parameters. We used oocyte diameter to determine reproductive stages and the condition index to describe the physiological state of oysters. Additionally, the temperature, salinity, seston and chlorophyll a were recorded at the study site. The results showed that C. gigas began accelerated reproductive activity in March under the influence of high temperature and increased concentrations of food. No spawning events were recorded and gametes were reabsorbed within the gonad in September and October. The results showed a period of nutrient storage during autumn–winter and another period of gamete production in spring–summer. A mortality event occurred at the end of winter, tied to significant increases in temperature and availability of food and in accelerated reproductive activity and high condition index. These conditions were very similar to those reported in other countries during summer die‐offs of C. gigas.

Twelve groups of 10 g turbot were fed ad libitum for 42 days. Each group was given a diet containing 37.5, 48.3, 59.2 or 69.8% protein, and 10, 15 or 20% lipid. Food consumption was similar for all diets. Specific growth rate (SGR) increased and feed conversion (FC) decreased with increasing dietary protein content. The best SGR (2.5%) and the best FC (0.57) were obtained with the 69.8% protein‐10% lipid diet. Lipid had a negative effect on growth and food conversion except for low protein diets. Carcass protein and lipid content were not influenced by diet composition. Liver lipid content was nearly constant and showed no trend in relation to the diet composition for 15 and 20% dietary lipid. The fish fed the 10% lipid diet showed higher liver lipid content. Liver glycogen increased with decreasing dietary protein content. High dietary protein levels enhanced daily tissue protein deposition. With the exception of the 37.5% protein‐20% lipid diet, which showed the best protein efficiency ratio (PER=3.1%) and the best protein utilization coefficient (PUC=50%), all the other diets gave similar PER and PUC values, from 2.2 to 2.6% and from 36 to 43%, respectively.

Nodipecten (Lyropecten) subnodosus (Sowerby 1835), the largest pectinid in tropical waters, has been continuously exploited. In support of sustainable development for this species, we started basic growth studies to establish aquacultural practices. N. subnodosus was cultured using triangular plastic cages in La Paz Bay (1995–1996) to describe growth and survival; we determined relationships between quantity of available food and growth and behaviour of body component indices. This culture system allows an isometric shell growth of scallops over 13 months; 56.8±2.1 mm height, 54.5±2.1 mm length and 23.0±1.1 mm width. Allometric growth was found between weight and height, length and width (survival was 44.3%). Body component indices and growth increased progressively until the summer of 1996 when all indices decreased negatively, influenced by high water temperatures. Gonad tissue developed during the first year. Gametogenic activity was evident, presenting the first spawn in summer. Particulate organic and inorganic matter and chlorophyll concentrations were relatively constant during the study, and there was no evidence relating these values to growth and body component indices. Culture of N. subnodosus is feasible in La Paz Bay. However, high water temperatures in summer reduced growth and survival rates.

A growth study of Pinctada mazatlanica and Pteria sterna was conducted to explain the basic steps required for the development of a pearl culture program in México. Seed for both species was collected using onion bags filled with black polyethylene sheets (40 ± 80 cm) and 5 g of vexar filament. The spatfall was July‐August 1987 for P. mazatlanica and December 1987‐February 1988 for P. sterna. The seed (12.8 ± 1.2 and 13.0 ± 0.6 mm respectively) was placed in pearl‐nets for intermediate culture (to attain 30 mm height). Populations were subsequently divided into three groups, two groups at 10 m depth in lantern and pocket nets and a third placed over a submerged shelf at 10 m depth in plastic net cages. Growth in height, survival and temperature were monitored. After 22 mo P. mazatlanica showed no significant differences in growth between culture structures. Nevertheless, the survival obtained in cages (99%) was larger than that obtained in hanging structures (65%). After 18 mo of culture, significant differences (F = 5.199 P = 0.05) in growth were observed for P. sterna. Larger animals were found in pockets (106.6 ± 0.8 mm) followed by lanterns (104.0 ± 0.7 mm) and finally in cages (103.5 ± 0.6 mm). Survival in pockets was 99%, 84% in lanterns and 98% in cages. With the operation of the different culture structures used in this study, the bottom cage system seems optimal to begin a culture program to obtain pearl‐oysters for nucleus implantation.

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