Annual distribution and abundance of Ceratium dens (Peridinales: Ceratiaceae) in the Gulf of California, Mexico

Ceratium dens distribution in the Gulf of California was studied based on three oceanographic campaigns, monthly abundance (1995-96) and during three red tide events in Mazatlán Bay. 52 phytoplankton samples with a Bongo net and 64 microns mesh light, during the year 120 water samples with a van Dorn bottle were collected in two sampling stations and from three red tide events. All samples were counted by the inverted-microscope method. The results showed that C. dens was present in the upper Gulf of California and surroundings of Cabo San Lucas. Two peaks were observed during spring and autumn in Mazatlán Bay during 1995-1996. The highest densities (20-360 cells.-l-1) were observed in coastal areas, whereas the lowest densities (1-14 cells.-l-1) were recorded in the open sea. During red tide events in 1985, 1989 and 1997, 144,000-256,000 cells.-l-1, 100,000-400,000 cells.-l-1, and 189,000-592,000 cells.ul-l was observed, respectively. During the red tide events C. dens varied, although sometimes was replaced by Skeletonema costatum or Pseudonitzchia spp and Ceratium furca. C. dens, seems to prefer areas with high productivity.     

Linking fish consumption patterns and health risk assessment of mercury exposure in a coastal community of NW Mexico

We aimed at characterizing the methylmercury (MeHg) exposure through fish consumption in two populations (common general and fishing-related population (FRP)) using a probabilistic health risk assessment in children, women of childbearing age, and adults in Mazatlán. The hazard quotients (HQs) were obtained from fish consumption, defined through a survey, and the levels of mercury in fishery products, obtained from published information. The average fish ingestion rate (IR_food) was higher in the FRP (167.85 g d^?1) than in the general population (GP) (140.9 g d^?1). However, HQs were significantly (p < 0.05) higher in the GP (ranging from 0.18 to 10.91) compared to the FRP (0.20 to 2.48); significant differences were also found among groups of both populations. Remarkably, children in both populations exhibited the highest proportions of risk, reaching up to 97% in GP. For all populations, fish consumption was the most important variable influencing MeHg exposure. Overall, for MeHg exposure, there is no safe level of fish consumption without risk, and actions should be taken to mitigate possible risk; further research with current data is needed to assess potential health risks associated with MeHg exposure, particularly in children.     

Length–weight and length–length relationships for some continental fishes of northwestern Baja California, México

Length–weight and length–length relationships were estimated for 10 freshwater, estuarine and marine fish species caught at the mouths of coastal sterams from northwestern Baja California (Mexico). The parameter b estimated by nonlinear least squares of weight and length data, ranged from 2.50 to 3.61. Size conversions (calculated total length from standard length) can be used in fishery for understanding several aspects of population dynamics.     

Condition status of the endangered desert pupfish,Cyprinodon macularius Baird and Girard, 1853, in the Lower Colorado River Basin (Mexico)

The length‐weight relationship (LWR) was used to test differences in the fish somatic condition factor among four populations of the endangered desert pupfish, Cyprinodon macularius, from the Lower Colorado River Basin, Mexico. Bimonthly fish sampling and habitat assessments were carried out from September 1996 to August 1997 for four sites in Baja California and Sonora. Slope b of the WLR varied from 3.238 (Cerro Prieto population) to 3.613 (Welton‐Mohawk population), showing in all populations a positive allometric growth. Male b values were higher than those of females for Cerro Prieto (3.303 vs 3.071), Welton‐Mohawk (3.866 vs 3.579), and Flor del Desierto (3.357 vs 3.169) populations. The Cerro Prieto population showed the highest somatic condition (y‐intercept, a = ?11.759). Water depth and salinity were the ecological variables that better accounted for most of the variation in the somatic condition of this pupfish, with a negative and a positive effect, respectively.     

Factors influencing the postweaning reproductive performance of sows on commercial farms

The objective of this study was to investigate the effects of various factors, including lactational feed intake, on the reproductive performance of sows in commercial herds. The 4 measures of reproductive performance were weaning-to-first-service interval, weaning-to-conception interval, litter weight at weaning, and subsequent litter size. Parity, farrowing season, lactation length, farrowing-to-conception interval, litter size, and lactation feed intake were investigated as risk factors common to the 4 measures of post-weaning reproductive performance. Using 4 basic multiple regression models for each measure, the least-square means for sets of factors were compared using the GLM procedure of SAS. Parity 1 sows had the longest weaning-to-first-service interval and weaning-to-conception interval, and the lighter litter weight at weaning (P < 0.05) than mid-parity sows. Sows in Parities 2 to 5 had larger subsequent litter size (P < 0.05) than those in Parities 1 and >/= 7. Sows farrowing in summer and spring had the longest and second longest weaning-to-conception interval (P < 0.05), respectively, while sows farrowing in summer had longer weaning-to-first-service interval than those that farrowed in spring (P < 0.05). Sows farrowing in summer produced the lightest litter weight at weaning (P < 0.05). No differences in subsequent litter sizes were found due to farrowing season (P > 0.10). As lactation length increased, weaning-to-first-service interval and weaning-to-conception interval decreased, and litter weaning weight increased. Longer lactation length and farrowing-to-conception interval were associated with larger subsequent litter size (P < 0.05). Litter size did not affect weaning-to-first-service interval or weaning-to-conception interval. Larger litter sizes were associated with heavier litter weight at weaning. Greater lactation feed intake improved the 4 measures of reproductive performance.     

PHENOTYPIC PLASTICITY INDUCED IN TRANSPLANT EXPERIMENTS IN A MUTUALISTIC ASSOCIATION BETWEEN THE RED ALGA JANIA ADHAERENS (RHODOPHYTA,CORALLINALES) AND THE SPONGE HALICLONA CAERULEA (PORIFERA: HAPLOSCLERIDA): MORPHOLOGICAL RESPONSES OF THE ALGA1

The association between the red macroalga Jania adhaerens J. V. Lamour. and the sponge Haliclona caerulea is the most successful life‐form between 2 and 4 m depth in Mazatlán Bay (Mexican Pacific). J. adhaerens colonizes the rocky intertidal area and penetrates into deeper areas only when it lives in association with H. caerulea. The aposymbiotic form of the sponge has not been reported in the bay. To understand the ecological success of this association, we examined the capacity of J. adhaerens to acclimate in Mazatlán Bay using transplant experiments. The transplanted aposymbiotic J. adhaerens did not survive the first 2 weeks; however, J. adhaerens when living in association with H. caerulea, acclimated easily to depth, showing no sign of mortality during the 103 d of the experiment. We conclude that the ability of J. adhaerens to colonize in deeper areas in this hydrodynamic environment may in part rely on the protection provided by the sponge to the algal canopy. Both species contribute to the shape of the associated form. Nevertheless, the morphological variation in the association appears to be dominated by the variation in J. adhaerens canopy to regulate pigment self‐shading under light‐limited conditions and/or tissue resistance under high hydrodynamics. Consequently, our results are consistent with light as the abiotic controlling factor, which regulates the lower depth distribution of the association in Mazatlán Bay, through limiting the growth rate of J. adhaerens. Hydrodynamics may determine the upper limit of the association by imposing high mass losses.     

Caliper and ultrasonographic measurements of bovine testicles and a mathematical formula for determining testicular volume and weight in vivo

This study quantified the relationship between calibrated caliper and ultrasonographic derived measurements of bovine testicles in vivo with actual testicular length, width, volume and weight. The prolate spheroid formula was tested to accurately predict testicular volume and a modification to predict weight. Ten bulls were employed to derive caliper and ultrasound testicle (n = 20) length and width measurements in vivo. Caliper length measurements were more reliable than ultrasound derived lengths, with correlations of r2 = 0.8023; P < 0.05 and r2 = 0.5111; P < 0.05, respectively. Width for both the calipers and ultrasound measurements when compared to actual width measurements were r2 = 0.7313; P < 0.05 and r2 = 0.8310; P < 0.05, respectively. The prolate spheroid formula is reliable in determining testicle (n = 116) volume (r2 = 0.8928; P < 0.05). Testicular volume and weight are highly correlated (r2 = 0.9776; P < 0.05); therefore, a modification of the prolate spheroid formula was used to predict weight (r2 = 0.9084; P < 0.05) against the actual weight. Caliper-derived length and width measurements used in the prediction of volume and weight had correlation coefficients against actual volume and weight of r2 = 0.5497; P < 0.05 and r2 = 0.6340; P < 0.05, respectively. Ultrasound in vivo measurements for prediction of testicular volume and testicular weight had a correlation of r2 = 0.3276; P < 0.05 and r2 = 0.6249; P < 0.05, respectively. A testicular (n = 116) length to width ratio of 1.8:1 (SEM = 0.01) was determined for both slaughterhouse and castrated animals. Caliper measurements are reliable, inexpensive and much simpler to obtain than ultrasound determinations for in vivo testicle length, width, volume and weight. The two-dimensional measurement of length and width would be a more accurate predictor of testicle volume and weight than the one-dimensional measurement of scrotal circumference (SC), especially in bulls with variation in testicular shape.     

Age,growth and reproduction in creole perch (Percichthys trucha) in the Negro River,Argentinean Patagonia

Age, growth and reproductive characteristics of creole perch, Percichthys trucha, were investigated in the Negro River, southern Argentina from samples collected seasonally, December 1994–December 1995. Age was estimated via scale and whole otolith reading methods. Total length (n = 413) ranged from 103 to 432 mm, and weight from 12 to 1042 g. Significant differences between the length‐weight relationships of males and females were detected (P < 0.05). Isometric growth was observed in juveniles and males, whereas total population and females exhibited positive allometric growth. The marking pattern in scales and otoliths followed an annual rhythm, with the formation of only one annulus in scales and only one hyaline band in otoliths during autumn‐winter. The oldest males were 5 years old whereas maximum age in females was 12 years from scales and 15 years from otoliths. Because scales were found to underestimate age in individuals older than 4 years, otoliths were considered to be the best structures for creole perch age determination. Gompertz growth parameters based on otolith data were L∞: 428.0 mm, k = 0.46 and t₀ = 0.43 for total population (r = 0.90), L∞: 410.7 mm, k = 0.42 and t₀ = 0.46 for males (r = 0.91), and L∞: 434.1 mm, and k = 0.49 and t₀ = 0.43 for females (r = 0.91). Lengths at first maturity (TL₅₀) were 260 and 241 mm in males and females, respectively, both of which corresponded to ages between 1 and 2 years. Macroscopic gonad inspection and the high percentage of juveniles captured during summer indicated that spawning begins at the end of spring.     

Length–weight relationships and length at first maturity for fish species in the upper Miranda River,southern Pantanal wetland,Brazil

Length–weight relationships (LWR) were estimated for 17 species and total length at first maturity (L50) for three species of freshwater fishes from the Miranda River, southern Pantanal, Brazil. The b values were compared for some species in the Paraguay River basin with the northern (Cuiabá River) part of the basin; differences in length–weight relationships were significantly different for Pseudoplatystoma corruscans, P. reticulatum (syn. P. fasciatum). First references on L50 and LWR are presented for two and eight fish species, respectively, as well as the new maximum total length for two species.     

New microsatellite loci for estimating genetic diversity and structure in Octopus hubbsorum from Nayarit,México

Background

Octopus hubbsorum Berry, 1953 is the most important species for commercial fishing in the Mexican Pacific. However, there is a lack of information regarding population structure that could have important management implications. We tested 44 microsatellite loci in O. hubbsorum by cross-amplification from O. bimaculatus.

Methods and results

Genetic diversity and structure was tested over 30 octopus sampled from Santa Cruz de Miramar (Nayarit, México). A total of 11 loci were successfully amplified. All loci were polymorphic with the number of effective alleles ranging from 2.13 to 23.14, while three loci significantly deviated from Hardy-Weinberg equilibrium. No significant LD was observed between pairs of loci (P?≥?0.05). The application of the new markers in a O. hubbsorum population from Santa Cruz de Miramar Nayarit, México, did not showed Wahlund or isolate breaking effects due to the mixing of distinct populations.

Conclusions

The loci were useful to estimate levels of pairwise relatedness and to discard the presence of recent demographic bottlenecks in the population. We consider that eight microsatellites are adequate from the 11 amplified loci

     

Stock characteristics of shovelnose sturgeon in the lower Platte River, Nebraska

The objectives of this research were to evaluate the condition, size structure, and growth of shovelnose sturgeon (Scaphirhynchus platorynchus) in the lower Platte River, Nebraska. A total of 1338 shovelnose sturgeon was collected using drifted gill and trammel nets (n = 954), trot lines (n = 340), and benthic trawls (n = 44) in the spring, summer, and autumn from four reaches: (i) Two Rivers State Park, (ii) confluence of Platte and Elkhorn rivers (iii) Louisville, Nebraska, and (iv) confluence of Platte and Missouri rivers during the spring, summer, and autumn of 2000 through 2004. Structural and condition indices were compared among reaches and years. Incremental relative stock densities (RSD) for shovelnose sturgeon sampled throughout the entire lower Platte River were: stock‐quality (1), quality‐preferred (12), preferred‐memorable (82), and memorable‐trophy (5). Proportional stock values were >99 for all years. A significance was detected in RSD categories among reaches and years with larger length‐categories observed in the upstream reaches. Mean relative weight (W_r) for all shovelnose sturgeon was 86.5, indicating a fit population. Mean W_r showed no significant differences among years, but significance was detected among reaches and RSD categories. Shovelnose sturgeon in the lower Platte River appear to be in good condition and exhibit different length‐frequency distributions longitudinally.     

黄海中南部细纹狮子鱼的生物学特征及资源分布的季节变化

根据2009年7—8月、10月和2010年1月、5月黄海中南部渔业生物底拖网调查数据,对该海域细纹狮子鱼的生物学特征及其分布的季节变化作了分析。结果表明,细纹狮子鱼平均体长和平均体重从春季(4.7 cm、3.3 g)到冬季(34.2 cm、764.9 g)呈显著增加,并且雄性个体平均体长显著大于雌性个体(P<0.05,春季除外)。性比(♀∶♂)随体长组和季节变化,体长越大趋向于雄性,反之趋向于雌性;夏季雄鱼居多(0.70∶1,P<0.05),秋季则为雌鱼居多(1.35∶1,P<0.05),而冬季(产卵群体)和春季性比接近于1∶1。细纹狮子鱼各季节摄食等级均在2.5以上,冬季雄性个体摄食等级显著大于雌性个体(P<0.05),但雄性个体肥满度为全年最低(1.52)。细纹狮子鱼相对资源量和贡献率从春季(0.17 kg/h,1.54%)到秋季(15.36 kg/h,33.05%)呈上升状态,而冬季(2.37 kg/h,5.60%)有所下降。相比2000年,夏秋季相对渔获量和贡献率提高明显。全年集中分布于7.8—13.6℃,3.20%—3.38%的水域,平均体重和水深有显著的相关性(秋季除外)。另外,根据性成熟个体分布区和稚幼鱼分布的相关历史资料分析发现,除海州湾外,黄海中部深水区可能是细纹狮子鱼的产卵场。     

The effect of host nutrition on itch mite, Psorergates ovis, populations and fleece derangement in sheep

Abstract. A group of thirty-two Merino sheep infested with itch mites (Psorergates ovis) and fed a maintenance diet which imposed moderate nutritional stress had a significantly higher mite population, significantly more skin scurf, and significantly more fleece damage or derangement (P < 0.05) than a second group of thirty-two infested sheep fed a diet designed for unrestricted body weight gain and wool growth. Histologically there were no significant differences between the groups in the numbers of mast cells, neutrophils or eosinophils observed in skin sections, but sheep that had high mite counts (>10 per 200 cm² of skin area) in both groups, had more dermal mast cells than sheep with fewer mites irrespective of the plane of nutrition. Skin thickness and greasy fleece weight in die group maintained on the low plane of nutrition were significantly less (P < 0.05) than in die well-nourished group, reflecting the difference in protein and energy content of the two diets. Within the nutritionally stressed group, the sheep with low mite counts had a significantly lower (P < 0.05) greasy fleece weight and a shorter mean staple length than the sheep with high mite counts. There was no significant difference in greasy fleece weight between sheep with low or high mite counts in the group fed on the high plane of nutrition.     

Developmental changes of carcass composition, meat quality and organs in the Jinhua pig and Landrace

The present study was aimed to compare the developmental changes of carcass composition, meat quality characteristics and organ weight in pigs of different breeds. Six pigs (sex balance) of each breed were slaughtered at 35, 80 and 125 days of age, respectively. The carcass was chilled and the left carcass side was dissected into bone, lean meat, fat and skin; additionally, organ weight and meat quality parameters were observed. Carcasses of the Jinhua pig were lighter (P < 0.001), contained less lean meat percentage (P < 0.01) and more carcass fat percentage (P < 0.05) than did carcasses of the Landrace. L*-values were lower in Jinhua pigs than in Landrace at 125 days of age (P < 0.05), but the Jinhua pig had higher a*-values compared with Landrace at the age of 80 days (P < 0.01) and 125 days (P < 0.01), respectively. In addition, Jinhua pigs showed lower colour scores (P < 0.05), higher intramuscular fat (IMF) percentage (P < 0.05), less marbling scores (P < 0.05) and lower drip loss (P < 0.05) than Landrace. For organ weight, Jinhua pigs had higher relative heart weight at the age of 80 days (P < 0.05) and 125 days (P < 0.001), and higher relative liver weight at 125 days of age (P < 0.01) than that of Landrace. In addition, the relative kidney weight was heavier (P < 0.001) in the Jinhua pig than in the Landrace during the whole experiment. These results indicated that developmental changes of carcass composition, meat quality parameters and organ weight displayed breed differences. Jinhua pigs were fatter than Landrace but the former had better quality characteristics in the meat.     

Migratory Masked Shrikes,Lanius nubicus staging at the desert edge: phenology,and sex- and age-related differences in body mass

Migratory Masked Shrikes (Lanius nubicus) were mist-netted during the spring and autumn migrations at Eilat, Israel. Nearly four times more shrikes were trapped during spring than in autumn. This could be explained by either the species assorting to loop migration, or a higher capture rate owing to poor body condition after crossing the Sahara in spring. In spring, no differences in phenology were observed between the sex- and age-groups. In contrast, in autumn juvenile males arrived significantly later than the rest of the population. Significant differences in wing chord length were found between the four sex and age classes (adult male, adult female, juvenile male, juvenile female) both in spring and autumn. However, significant differences in body mass were found only in autumn. In spring, in both sexes, wing length and body mass changed significantly with date of arrival. Masked Shrike in spring were lighter than in autumn. The results suggest that migration over desert is energetically costly and Eilat is a very important staging place for migratory Masked Shrikes.     

黄鳝体内寄生隐藏新棘虫和胃瘤线虫的频率分布及季节动态

寄生虫的感染会对黄鳝（Monopterus albus Zuiew,1793）造成不利影响,其中寄生其肠道的隐藏新棘虫（Pallisentis（Neosentis）celatus van Cleave,1928）和寄生于体腔的胃瘤线虫幼虫（Eustrongylidessp.）对黄鳝健康的影响尤其严重,研究调查了以上两种寄生蠕虫在黄鳝体内的频率分布以及季节动态。在连续23个月内共调查黄鳝1980尾,结果显示,隐藏新棘虫的感染率为34.46%,平均丰度为2.948.37,平均丰度与鱼类体长之间呈显著正相关关系（R=0.16,P0.05）,平均丰度和聚集度在42 cmL48 cm体长组达到最大值后开始下降,呈现凸形曲线。胃瘤线虫幼虫感染率为15.14%,平均丰度为0.612.45,平均丰度与鱼类体长之间呈显著负相关关系（R=-0.14,P0.05）,平均丰度在24 cmL30 cm体长组达到最大值后开始逐渐下降,聚集度是在30 cmL36 cm体长组达到最大值后开始下降。各月份间隐藏新棘虫的平均丰度和感染率都有显著性差异（F=10.50,P0.05;G=84.440.05222= 33.9）,感染主要发生在春季和秋季;胃瘤线虫幼虫各月份间的平均丰度和感染率也都有显著性差异（F=6.70,P0.05;G =143.88 0.05222= 33.9）,感染主要发生在春末夏初。       

Age at puberty, ovulation rate, uterine length, prenatal survival and litter size in Chinese Meishan and Yorkshire females

Studies on the ovulation rate, prenatal survival and litter size of Chinese Meishan pigs have given widely divergent results depending on the extent of inbreeding of the animals, their original genetic diversity, the age and parity, and the conditions of management. To obtain meaningful results, it is necessary to characterize the population under study. The following report characterizes populations of Meishan and Yorkshire of a widely diverse background. First farrowing data were collected on 21 Meishan and 20 Yorkshire gilts. Meishan gilts had 12.4 fully formed piglets and Yorkshire gilts had 7.4 fully formed piglets (P < 0.01). Meishan gilts averaged 1.86 mummified fetuses per litter vs 0.05 per Yorkshire litter (P < 0.01). Yorkshire piglets averaged 1.3 kg body weight at birth vs 0.9 kg for Meishan piglets (P < 0.01). At 47 days of second gestation, 19 Meishan and 12 Yorkshire sows averaged 22.7 and 16.3 corpora lutea (CL), respectively (P < 0.01). Uterine length and number of fetuses were not different (P > 0.40) in the two breeds. Daily estrous detection of 50 Meishan and 34 Yorkshire gilts began at 60 and 120 days of age, respectively. Meishan gilts reached sexual maturity at 95 days of age, which was 105 days earlier than Yorkshire gilts (P < 0.01). Meishan gilts were in estrus nearly 1 day longer than Yorkshire gilts at first, second and third estrus (P < 0.05). No differences in cycle length between breeds were detected for the first or second estrous cycle (P > 0.60). Nineteen Meishan gilts were slaughtered at 51 days of gestation and their reproductive tracts were recovered. The mean number of dissected CL (17.0), number of fetuses (13.1), total uterine length (396 cm), spacing per fetus (29.9 cm), allantoic (124.9 ml) and amniotic (32.2 ml) volumes, crown-rump length (82.8 mm), weight (35.4 g), sex, and direction of each fetus were determined. Chinese Meishan gilts reached puberty much earlier and were in estrus longer than Yorkshire gilts and Meishan sows had more CL than Yorkshire sows.     

Frond elongation rates of shallow waterMacrocystis pyrifera (L.) Ag. In northern Baja California,Mexico

Macrocystis pyrifera (L.) Ag.frond elongation rates were measured during autumn-winter, spring and summer in a shallow water (7.5 m depth) kelp bed in Bahía Papalote, northern Baja California. Frond elongation was maximum during spring and minimum during winter. Frond growth was significantly correlated with solar radiation, and was highest in the smallest size fronds (0–2 m). Average frond elongation rate varied between 0.3–11% d^–1 during the study period. The relationship between average frond length and elongation rate followed an exponential curve with a negative slope during autumn-winter and summer, but was best described by a straight line during spring. Standard growth rates were obtained by a graphic method. Standard growth rates had intermediate values between those reported for southern California and southern Baja California.M. pyrifera growth cycle shows a different trend from what has been previously reported.     

Rearing management of rabbit males selected by high growth rate: the effect of diet and season on semen characteristics

A total of sixty-six young males were used to evaluate the effect of low (L), medium (M) and high (H) concentrations of dietary digestible energy received during the rearing seasons (autumn and spring) on the performance and main semen characteristics of males for artificial insemination selected by a high growth rate. Males reared during the spring season presented a significantly higher weight at weaning than those reared during the autumn season (P < 0.001), and these differences were maintained until the end of the trial. The requirements of the males were easily covered as a general rule. In the autumn group, the males were unable to intake the digestible protein recommended only during their 3rd month of life, especially with low concentrate diets (P < 0.05). H males showed higher semen concentration and production during the autumn season, while L males showed a higher semen concentration and production than M males during the spring season, the H group showed intermediate values (P < 0.001). Males reared during the spring season showed significantly higher values of sperm concentration (P < 0.01) and production (P < 0.01). H males presented a lower percentage of spermatozoa with cytoplasmic droplets than the L group (P < 0.05) and the lowest values for sperm abnormalities during the autumn season, while the L group presented higher values for percentage abnormalities, especially during the last month controlled (P < 0.05). As a general rule, the main motility parameters controlled were not affected by the rearing diet received nor the season. These results seem to indicate that the management of rabbit males during the growing and rearing periods seem to significantly affect their subsequent performance and semen production.