Summer microhabitat use by adult and young‐of‐year snail darters (Percina tanasi) in two rivers

Ashton MJ, Layzer JB. Summer microhabitat use by adult and young‐of‐year snail darters (Percina tanasi) in two rivers. Ecology of Freshwater Fish 2010: 19: 609–617. © Published 2010. This article is a US Government work and is in the public domain in the USA. Abstract – We characterised microhabitat availability and use by adult and young‐of‐year (YOY) snail darters (Percina tanasi Etnier 1976 ) while snorkelling in the French Broad and Hiwassee rivers, TN, USA. Both age groups of snail darters disproportionately used most microhabitat variables compared to their availability. Snail darters primarily occupied moderately deep, swift water over gravel substrates with little macrophyte coverage and no silt. Univariate comparisons indicated that adult and YOY darters occupied different habitat, but there was no marked differences between principal components analysis plots of multivariate microhabitat use within a river. Although the availability of microhabitat variables differed between the French Broad and Hiwassee rivers, univariate means and multivariate plots illustrated that the habitats used were generally similar by age groups of snail darters between rivers. Because our observations of habitat availability and use were constrained to low flow periods and depths <1 m, the transferability of our results to higher flow periods may be limited. However, the similarity in habitat use between rivers suggests that our results can be applied to low‐normal flow conditions in other streams.     

Biological traits of eastern sand darter (Ammocrypta pellucida) in the lower Thames River,Canada, with comparisons to a more southern population

Eastern sand darter (Ammocrypta pellucida) is listed as Threatened under the Canadian Species at Risk Act. Little relevant biological information is available for most Canadian populations and only limited information is available for populations in the United States. To supplement the paucity of information, this study collected biological information on eastern sand darter during field surveys in 2006–2007 from 10 sites in the lower Thames River, Ontario, Canada. Collected data were used to estimate critical life history traits including: longevity, fecundity, clutch size and number, growth, survival, age‐at‐first‐maturity and cohort age structure. Longevity was 3+ years, with age‐at‐first‐maturity being 1+ for both sexes. Examination of egg sizes from preserved females in 2007 showed a bimodal distribution, suggesting two spawning occurrences of 71 eggs each. Quantitative comparison of lower Thames River biological information with a more southerly eastern sand darter population in the Little Muskingum River, Ohio, demonstrated little variation between the populations. Data comparisons suggest that localised environmental factors are affecting biological traits (growth), in particular water temperature that may be controlled by differences in riparian cover and/or groundwater input.     

Microhabitat use by fish in the lower Rio Matarraña, Spain, 1984–1987

We quantified microhabitat use in Barbus graellsii, Cyprinus carpio, Chrondostoma toxostoma, Esox lucius, Gobio gobio and Leuciscus cephalus during 1984–1987 in the lower Rio Matarraña, Spain. Fluctuations in numerical abundances of assemblage members increased during 1986–1987. These increased fluctuations were due to decreases in the abundances of Ch. toxostoma, E. lucius and G. gobio during the latter 2 years of our study. Only C. carpio increased slightly in abundance during this period. An analysis of microhabitat availability data indicated that 16 seasonal samples could be assigned to 1 of 6 groups ranging from: seasons with zero velocities, shallower depths and an algal/debris substratum to those with high velocities and depths and a substratum composed of algae/debris, rubble and gravel. Most seasonal changes in the substratum were attributable to conditions inhospitable to the growth of benthic algae (i. e., high velocities or low oxygen levels) rather than to actual changes in the underlying lithospheric substratum. Principle component analyses indicated that most species were overrepresented in deeper microhabitats with depositional substrata. Ch. toxostoma, however, tended to occur over rubble substrata in both shallow and deep microhabitats. Most seasonal changes in microhabitat use were produced by seasonal variations in microhabitat availability. However, all species except E. lucius exhibited seasonal variations in microhabitat use that typically involved velocity, depth and substratum composition. Although smaller specimens of most species were found closer to the substratum in 1984–1985, they tended to occupy shallow areas in 1986–1987. Canonical analyses of discriminants and univariate data demonstrated that the distance from the substratum was the best predictor of interspecific differences in microhabitat use. Species could be arrayed along a vertical gradient with L. cephalus and Ch. toxostoma occupying mid-water column positions, B. graellsii and C. carpio occurring in lower-water column microhabitats and E. lucius and G. gobio strongly associated with the substratum. Changes in interspecific microhabitat use were not correlated with changes in species abundances, and hence, interspecific competition did not appear to strongly influence microhabitat use during our study.     

Microhabitat use by fish in the upper Rio Matarraña, Spain, 1984–1987

Abstract– We evaluated the microhabitat use and abundance of Barbus graellsii, Bardus haasi, Chondrostoma toxostoma, Noemacheilus barbatulus, Oncorhynchus mykiss and Rutilus arcasii between 1984 and 1987 in the upper Rio Matarraña, Spain. The mean abundance classes for all species ranged from 1.8 to 3.0 (where 1=1–6, 2=6–10, 3=11–20 and 4=>20 specimens, respectively). Mean abundance was consistently higher in 1984–1985 (2.4–3.0) than during 1986–1987 (1.8–2.8). The decreases noted in 1986–1987 were attributable to declines in abundance of O. mykiss (introduced in winter 1984) and B. haasi. Barbus graellsii and Ch. toxostoma, however, remained abundant throughout the entire 4-year study. We only observed N. barbatulus and R. arcasii irregularly in the study site. Analyses of microhabitat availability data indicated that the study site contained more silt and less algae/debris during spring 1985 and early and late summer 1986 than in the majority of the remaining season. The converse was true for late summer 1985 (i. e., less silt and more algae/debris than the majority of seasons). Principal component analyses showed that B. graellsii and Ch. toxostoma generally occupied deeper microhabitats with low to average velocities, higher amounts of depositional substrata and lower quantities of erosional substrata. B. haasi tended to avoid microhabitats with rubble substrata and occurred in those with higher amounts of algae/debris. O. mykiss occupied shallower areas with slightly higher velocities and a heterogeneous substratum. With the exception of B. haasi, microhabitat use by assemblage members was similar from 1984 to 1987. B. haasi, however, was not as strongly affected by depth in the latter two years of the study as it was during 1984–1985. Seasonal and annual analyses of intraspecific microhabitat use showed that most changes were due to variations in microhabitat availability. Nonetheless, all species exhibited minor seasonal shifts in microhabitat use. Size-related analyses indicated that both smaller B. graellsii and Ch. toxostoma occupied shallower microhabitats with slower velocities than larger specimens. Intersite differences in microhabitat use for B. graellsii and Ch. toxostoma showed that most differences in substratum use were attributable to disparities in substratum availability. Both species occurred closer to the substratum in the site with higher velocities (i. e., upper reach), although this response was more pronounced in Ch. toxostoma. Interspecific analyses indicated that B. graellsii and Ch. toxostoma did not consistently occupy statistically differentiable microhabitats, although both species occurred farther from the substratum and refuges than did B. haasi. O. mykiss occupied shallower microhabitats with more gravel than either B. graellsii or Ch. toxostoma. The lack of microhabitat shifts by native species during the study period indicates that interactions with either B. haasi or O. mykiss did not play a strong role in microhabitat use by the remaining assemblage members.     

Microhabitat use by Iberian nase Chondrostoma polylepis and Iberian chub Squalius carolitertii in three small streams, north-west Portugal

Abstract –  Microhabitat use of Iberian nase Chondrostoma polylepis (Steindachner 1865) and Iberian chub Squalius carolitertii (Doadrio 1988) was studied in three small streams of the Lima basin, north-west Portugal. Measurements were made for 210 and 248 individuals, respectively, distributed in two size classes, based on fish ages, during winter, spring, summer and autumn 1998. Both species moved to shallow and slow-flowing microhabitats in summer and autumn, but this mainly reflected seasonal variation in microhabitat availability. Larger individuals of both species used deeper and lower percentage cover areas than smaller conspecifics, however significant ontogenetic differences were only found for water velocity. Different patterns of nonrandom microhabitat use were displayed by both cyprinids. Larger I. nase were in deeper and more discovered waters than those available in the habitat, whereas I. chub was over-represented in slow-flowing areas. There was no evidence of interspecific competition for microhabitat, therefore it is unlikely that spatial resource was limited during the present study.     

Pathogenic threats and probiotic use in larviculture of the scallop,Pecten maximus

During a series of experiments, bacteriological elements in scallop larval rearing were investigated: larvae susceptibility to pathogens as a function of their age, and the use of probiotic bacteria during larviculture. Younger larvae (d5 PF) were highly more susceptible to pathogenic‐challenge than their older siblings, which were challenged at an older age (d15 PF). A challenge with 10⁴ CFU mL^?1 of V. pectenicida killed 100% of d5 PF larvae 7 days following challenge, yet killed only 9% of d15 PF larvae 9 days following challenge. Use of the probiotics Phaeobacter gallaeciensis, Alteromonas macleodii 0444 and Neptunomonas sp. 0536, provided for larger larvae, a high yield of competent larvae and, perhaps more importantly, protection against pathogen‐challenge similar to levels achieved from antibiotic use. When challenged with V. pectenicida, d29 survivals were 20.3%, 85.1% and 75.0% respectively for control (no probiotic), antibiotic treated, and ‘probiotic mix’ administered larvae. Use of potential probiotic Pseudoalteromonas sp. D41 appeared to hinder scallop larvae. Future use of probiotics in scallop larval rearing would benefit from combined use of P. gallaeciensis, A. macleodii 0444 and Neptunomonas sp. 0536.     

Beaver dams shift desert fish assemblages toward dominance by non‐native species (Verde River,Arizona, USA)

The reintroduction of beaver (Castor canadensis) into arid and semi‐arid rivers is receiving increasing management and conservation attention in recent years, yet very little is known about native versus non‐native fish occupancy in beaver pond habitats. Streams of the American Southwest support a highly endemic, highly endangered native fish fauna and abundant non‐native fishes, and here we investigated the hypothesis that beaver ponds in this region may lead to fish assemblages dominated by non‐native species that favour slower‐water habitat. We sampled fish assemblages within beaver ponds and within unimpounded lotic stream reaches in the mainstem and in tributaries of the free‐flowing upper Verde River, Arizona, USA. Non‐native fishes consistently outnumbered native species, and this dominance was greater in pond than in lotic assemblages. Few native species were recorded within ponds. Multivariate analysis indicated that fish assemblages in beaver ponds were distinct from those in lotic reaches, in both mainstem and tributary locations. Individual species driving this distinction included abundant non‐native green sunfish (Lepomis cyanellus) and western mosquitofish (Gambusia affinis) in pond sites, and native desert sucker (Catostomus clarkii) in lotic sites. Overall, this study provides the first evidence that, relative to unimpounded lotic habitat, beaver ponds in arid and semi‐arid rivers support abundant non‐native fishes; these ponds could thus serve as important non‐native source areas and negatively impact co‐occurring native fish populations.     

Evaluation and characterization of a novel probiotic Lactobacillus pentosus PL11 isolated from Japanese eel (Anguilla japonica) for its use in aquaculture

In the present study, a potential Lactobacilli probiotics were isolated from Japanese eels (Anguilla japonica) and characterized and evaluated for their possible use in eel farming. Sixteen Lactobacilli were isolated from intestines of Japanese eels, using selective media. The lactobacilli strains (represented as PL1 to PL16) were screened by their ability to produce digestive enzyme. Among these, three strains (PL11, PL13 and PL16) producing four digestive enzymes (amylase, cellulase, protease and phytase) simultaneously were characterized further using API ZYM kit. From these, PL11 (Lactobacillu (L.) pentosus) was identified as potential probiotics candidate producing 15 enzymes among 20 tested. Further examination of biological activities of PL11 revealed tolerance against pH, artificial bile juice and antibacterial activity against several fish pathogenic bacteria. The in vitro competitive exclusion assay also revealed 88.4% reduction in adhesion of fish pathogen (Edwardsiella tarda) by PL11 to host intestinal mucus. In vitro incubation of Japanese eel foregut with Baclight‐labelled PL11 showed colonization of the enterocyte surface by confocal and scanning electron microscopy. In summary, PL11 isolated from eels could serve as a potential probiotics with acid and bile tolerance, production of digestive enzymes, antibacterial activity and inhibition of fish pathogen adhesion to intestinal mucus.     

The use of diatom Skeletonema costatum on aquaculture‐produced purple sea urchin (Paracentrotus lividus) larvae and post‐larvae diet

The quality of the microalgae provided on Paracentrotus lividus larvae rearing is a primordial factor having a direct (nutritional properties) and indirect (water quality) impact on growth, competence and survival. Skeletonema costatum is a diatom commonly used in the bivalve cultivation. However, the use of this diatom in P. lividus larval cultivations is poorly known. The Rhodomonas spp. is a microalgae commonly used in sea urchin larvae culture. Three different diets were tested on P. lividus larvae and post‐larvae cultivation (D1—Rhodomonas marina, D2—S. costatum, D3—mixture of both algae). Larvae fed with the D2 diet (55.8%) and D3 (39.9%) had a survival at 15 DAH higher than D1 (5.5%). The low survival in D1 could be due to the higher microbiological load on microalgae (Vibrio alginolyticus and V. pectenicide). Larvae fed with S. costatum (D2) showed a lower development than other diets. The competency index was lower for larvae fed with the D2. These results show that microalgae diversified diets contribute to a better development of P. lividus larvae. During the settlement and post‐settlement phase, there was also a lower growth of the sea urchin fed with the D2 and a higher survival for D3.     

A comparison between water exchange and settling tank as a method for suspended solids management in intensive biofloc technology systems: effects on shrimp (Litopenaeus vannamei) performance,water quality and water use

Biofloc systems rely on microbial processes in the water column to recycle animal waste products, reducing the need for water exchange. These increases biofloc concentration in the water and some form of removal is needed. An experiment was carried out to evaluate two management practices to control biofloc in Litopenaeus vannamei culture. Six tanks (48 m³) were divided into two treatments: water exchange and solid settler. Shrimp were stocked at 164 shrimp m^?2 and with 0.67 g of weight. After 61 days, shrimp under solid settler treatment demonstrated mean weight of 12.7 ± 0.5 g with survival of 73.8 ± 1.4%, and those under water exchange had a final weight of 10.1 ± 0.2 g and survival rate of 57.8 ± 11.1%. Total suspended solids did not differ between the treatments: 326.8 ± 24.9 mg L^?1 for water exchange and 310.9 ± 25.3 mg L^?1 for solid settlers. Settleable solids and productivity/respiration ratio was higher (P < 0.05) in water exchange treatment, indicating differences in physical and biological characteristics of bioflocs. Solids removal method influenced the water use, in which 1150 ± 249 L of water was necessary to produce one kilogram of shrimp using water exchange strategy, and 631 ± 25 L kg^?1 with the use of settlers. Our results indicate that continuous operation of settlers can reduce variability in solids characteristics and water quality variables such as ammonia. Both strategies are efficient in controlling biofloc concentrations of the water; however, settlers can reduce water use and improve shrimp production.     

Habitat partitioning among three predatory fish in a temperate reservoir

The diversity of predatory species plays a key role in ecosystem functioning but our understanding of the mechanisms underlying their coexistence is limited, particularly in freshwater ecosystems. Northern pike Esox lucius, European perch Perca fluviatilis and pikeperch Sander lucioperca are three widespread predatory species in European lakes, where they often coexist. As potential competitors, we hypothesised that partitioning habitat is a determinant of species coexistence. This was tested by quantifying the variability of their habitat use in tracking adult individuals in the Bariousses reservoir (France, 86.6 ha, mean depth 7.1 m). Specifically, we investigated their distribution along the littoral–pelagic and depth axes along the daily cycle and across seasons. From littoral to pelagic waters were first found pike, then perch and finally pikeperch. Pike was the closest to the surface while pikeperch was the deepest. This general pattern was, however, variable across seasons with the three species located in the upper layer in summer during reservoir stratification. Individuals were more evenly distributed along the littoral–pelagic axis and closer to the bottom when water was mixing (autumn, winter). In summer, perch used more intensively in the pelagic zone during the daytime. Other species did not show any diel change of habitats. Our results highlighted that species coexistence is associated with habitat partitioning among these three predators, with perch showing a more variable behaviour regarding habitat characteristics. Now more than ever, in the context of global change which modifies habitats, it is of crucial importance to understand the coexistence mechanisms of species that shape ecosystems.     

The effect of free ammonia nitrogen,pH and supplementation with oxygen on the growth of South African abalone,Haliotis midae L. in an abalone serial‐use raceway with three passes

The farming of abalone, Haliotis midae L., can be intensified in serial‐pass systems, but water re‐use increases the concentration of NH₃ (free ammonia nitrogen, FAN) and reduces water pH. Changing the percentage dietary protein from 33% to 26% reduced the concentration of FAN (F_{42, 252} = 2.79; P < 0.0001) in a serial‐pass system and did not reduce weight gain (F_{1, 12} = 1.09; P = 0.31) or length gain (F_{1, 12} = 1.08; P = 0.31). Low water pH was the most important variable to contribute to a reduction in abalone growth (weight gain: F_{1, 19} = 64.5; P < 0.0001; r² = 0.76; length gain: F_{1, 19} = 41.9; P < 0.0001; r² = 0.67). In addition, supplemental oxygen (103% saturation) improved length gain (t = 3.45, P = 0.026) in abalone exposed to an average FAN concentration of 2.43 ± 1.1 μg L^?1) and an average pH value of 7.6 ± 0.13, relative to a treatment with no oxygen supplementation. Thus, in an abalone serial‐use raceway with three passes, FAN was not the first growth‐limiting variable. It is suggested that future studies should examine the major causes of reduced water pH in serial‐use systems and their effect on the growth and health of H. midae.     

Microhabitat selection of Gyrodactylus salaris Malmberg on different salmonids

The microhabitat selection of the ectoparasite Gyrodactylus salaris (Lærdalselva strain, Norway) was investigated concurrently with studies on the parasite population growth on five strains of Atlantic salmon, Salmo salar L., and a strain of Danish rainbow trout, Oncorhynchus mykiss (Walbaum). The salmon used were hatchery‐reared parr of East Atlantic strains [River Conon (Scotland), River Storå (western Denmark) and River Ätran (western Sweden)] and Baltic strains [Lule and Ume (eastern Sweden)]. The location and numbers of parasites were recorded on anaesthetized fish once a week from week 0 to week 8. The mean abundance of G. salaris steadily increased to high levels on the River Conon, Storå and Ätran strains until the end of the experiment. The mean abundance of G. salaris on the two Baltic strains (River Lule älv and River Ume älv) initially increased but after 4–7 weeks the growth of the parasite infrapopulations decreased markedly. The Danish rainbow trout strain showed the lowest abundances of all the fish species and strains. Gyrodactylus salaris preferentially selected the fins and head region when colonising the hosts (all species and strains). Increasing percentages of G. salaris on the tail fins of the East Atlantic strains and rainbow trout were found during the course of infection, whereas the two Baltic salmon strains experienced a decreasing percentage of parasites in this microhabitat.     

Evaluation of dried macrophytes as an alternative diet for the rearing of the sea urchin Paracentrotus lividus (Lamarck, 1816)

The aim of this work was to assess the potential use of different dried macroalgae as food in the rearing of Paracentrotus lividus. Growth, consumption and food conversions were compared in adult sea urchins fed with fresh or dried thalli of four macroalgae species. Six experimental diets were tested: (a) fresh Palmaria palmata; (b) fresh Saccharina latissima; (c) dry P. palmata; (d) dry S. latissima; (e) dry Laminaria digitata and (f) dry Grateloupia turuturu. Linear growth rates were similar for all treatments. Specific growth rate was higher in sea urchins fed with fresh P. palmata, but no difference was found between animals fed with fresh S. latissima and those fed with dried diets. Regarding daily food consumption (DFC), sea urchins consumed the same amount of dried macroalgae as fresh but exhibited a higher food conversion efficiency (FCE) when fed with fresh P. palmata. However, this FCE was only significantly higher when compared to sea urchins fed with dry L. digitata. Dried G. turuturu is not a suitable diet due to its rapid degradation after rehydration. The results suggest that P. lividus adults can be reared on dried macroalgae thalli without detriment to their somatic growth, especially over short periods. The low cost of feeding sea urchins with this diet could help small shellfish farmers to diversify their production into echinoculture.     

The role of rpoS in the regulation of Vibrio alginolyticus virulence and the response to diverse stresses

Vibrio alginolyticus is a leading aquatic pathogen, causing huge losses to aquaculture. rpoS has been proven to play a variety of important roles in stress response and virulence in several bacteria. In our previous study, upon treatment with Cu²⁺, Pb²⁺, Hg²⁺ and low pH, the expression levels of rpoS were downregulated as assessed by RNA‐seq, while impaired adhesion ability was observed, indicating that rpoS might play roles in the regulation of adhesion. In the present study, the RNAi technology was used to knockdown rpoS in V. alginolyticus. In comparison with wild‐type V. alginolyticus, RNAi‐treated bacteria showed significantly impaired abilities of adhesion, growth, haemolytic, biofilm production, movement and virulence. Meanwhile, alterations of temperature, salinity, pH and starvation starkly affected rpoS expression. The present data suggested that rpoS is a critical regulator of virulence in V. alginolyticus; in addition, rpoS regulates bacterial adhesion in response to temperature, pH and nutrient content changes. These are helpful to explore its pathogenic mechanism and provide reference for disease control.     

Co‐Infection with Pseudomonas anguilliseptica and Delftia acidovorans in the European eel,Anguilla anguilla (L.): a case history of an illegally trafficked protected species

Inspections by customs agents at Barcelona airport discovered 420 kg of contraband glass eels prepared for shipment to Hong Kong. After confiscation of these animals by police, they were transported to holding facilities to be maintained until after a judicial hearing. Upon arrival, they were separated into two groups and held under ambient flow‐through conditions in fresh water. During their captivity period, several peaks in mortality occurred and multiple bacterial strains were isolated from moribund animals. Sequencing of 16S rDNA was used to determine specific identity of the isolates. An initial isolation of Pseudomonas anguilliseptica was treated with oxytetracycline. A subsequent isolation of Delftia acidovorans proved resistant to oxytetracycline and was treated with gentamicin in combination with sulphadiazine–trimethoprim. Once the health condition of the animals was stabilized, they were partitioned into groups and subsequently released as part of a restocking effort for the species following the guidelines of Regulation (EC) 1100/2007 (Anon 2007). This represents the first record for both bacterial species in the host Anguilla anguilla in the Spanish Mediterranean.     

Spat availability of commercial bivalve species recruited on artificial collectors from the northern Gulf of California. Seasonal changes in species composition

This study reports a year‐round recruitment of spat of four commercial bivalve species; Pteria sterna, Euvola vogdesi, Pinctada mazatlanica and Pinna rugosa collected in the region of Puerto Peñasco, north‐eastern coast of the Gulf of California. Bimonthly recruitment of commercial bivalve spat on netlon^® collectors was evaluated for six sites from June 2007 to August 2008. To describe spat recruitment abundances with environmental parameters, sea surface temperature (°C) and surface chlorophyll a concentration (mg m^?3) were characterized by means of monthly Aqua/MODIS satellite data. For each species a repeated measures anova was used to evaluate differences in the number of spat between months, sites and depths. Maximum sea surface temperature was recorded in August–September (~31.5°C) and the minimum in January–February (~15°C), while the minimum surface chlorophyll a was observed in June–September (mean range = 1.5–2 mg m^?3) and the maximum in January–March (mean range = 2–5 mg m^?3). Spat recruitment showed distinct patterns; P. sterna can be characterized as having a Winter–Spring pattern, E. vogdesi a winter pattern, while P. mazatlanica and P. rugosa a summer spat recruitment pattern. This information constitutes part of the fundamental data needed for the development of aquaculture and conservation initiatives in the region based on wild spat supply.     

Efficacy of calcein as a chemical marker of green‐lipped mussel (Perna canaliculus) larvae and its potential use for tracking larval dispersal

An optimal chemical shell marking protocol was developed for the New Zealand green‐lipped mussel, Perna canaliculus with a view to its future use in larval tracking experiments. Larval P. canaliculus aged either 10, 15 or 19 days post fertilization were immersed in treatments of 50, 100 and 200 mg L^?1 of calcein for a period of 24 h before measurements of shell mark brightness were taken. There was 100% marking success in all calcein treatments for all age classes, with 19‐day larvae immersed in 200 mg L^?1 calcein producing the brightest mark. Growth was not affected by calcein immersion; however, 10‐day larvae exhibited significantly higher levels of mortality compared with 15‐ and 19‐day larvae suggesting a reduced resilience to the marking protocols in younger larvae. In a mass staining experiment, a solution of 100 mg L^?1 calcein was used to successfully stain15.6 million hatchery reared P. canaliculus larvae. Calcein, therefore, offers a low impact method with which to stain the sensitive early life stages of this species thus providing a rapid method for identifying individuals of interest, i.e. individuals released in the wild or specific family lines within a hatchery environment.     

Increased gonad growth of the purple sea urchin (Strongylocentrotus purpuratus) fed the giant kelp (Macrocystis pyrifera) and the sea lettuce (Ulva lactuca) enriched with nutrients

Adult (Strongylocentrotus purpuratus) purple sea urchins were fed giant kelp (Macrocystis pyrifera) and sea lettuce (Ulva lactuca) macroalgae that were unenriched and enriched with nutrients. Urchins were fed over 10 weeks (5% body weight per day) under laboratory conditions to determine the effect of macroalgae species and treatment (enriched and unenriched) on growth, gonad index and gonad quality. Significant differences were observed when urchins were fed enriched Macrocystis pyrifera (MPE). Gonad weight increased from 0.7 ± 0.1 g (mean ± SD) to 5.9 ± 1 g, and gonad index increase from 3.5 ± 1.5% to 14.9 ± 2.3% over 10 weeks. Significant differences were also noted in gonad quality, and gonad colour and firmness were better in urchins that were fed unenriched M. pyrifera (MPUE) and MPE – whereas texture did not differ between M. pyrifera treatments and unenriched U. lactuca (ULUE). With regard to taste, gonads were sweeter in MPE‐fed individuals. Enriched U. lactuca (ULE) failed to grow gonads significantly; as a result, their quality was unacceptable for the market. These results suggest that S. purpuratus experience increased gonad production and quality in short periods when fed nutrient‐enriched M. pyrifera.