我国蟹类土池育苗技术研究进展

蟹类养殖产业已成为我国水产养殖的支柱产业之一。中华绒螯蟹(Eriocheir sinensis,以下简称河蟹)、三疣梭子蟹(Portunus trituberculatus,以下简称梭子蟹)、拟穴青蟹(Scylla paramamosain,以下简称青蟹)是我国主要的养殖蟹类。目前3种蟹类土池育苗技术发展不平衡,河蟹、梭子蟹土池育苗技术较为成熟,已经普及推广并在养殖生产中发挥重要作用;青蟹土池育苗尚未有成功的报道。本文综述了我国河蟹、梭子蟹、青蟹苗种生产技术,尤其是土池育苗技术的研究进展,并对河蟹、梭子蟹土池育苗关键技术进行分析,旨在探讨蟹类土池育苗技术应用于青蟹土池育苗的可行性。     

Effects of acute and chronic toxicity of unionized ammonia on mud crab, Scylla serrata (Forsskål, 1755) larvae

While the effects of ammonia on fish and prawn larvae are well documented, little is known of its effect on mud crab (Scylla serrata) (Forsskål, 1755) larvae. Two experiments were conducted in 5 L hemispherical plastic bowls, containing 3 L of ultra‐filtered and settled seawater and various larval stages of mud crab to (1) determine the acute median lethal concentration (LC₅₀) of unionized ammonia and (2) to determine the chronic effects of unionized ammonia on survival and percentage moulting to zoea and megalop stages. The larval stages that exhibited the highest tolerance to ammonia over 24 h were zoea 1 (LC₅₀ of 4.05 mg L^?1 of unionized ammonia) and zoea 5 (LC₅₀ of 6.64 mg L^?1 of unionized ammonia). The megalop stage had the lowest total ammonia LC₅₀ at both 24 and 48 h, making it the larval stage most susceptible to total ammonia. Exposure to 6.54 mg L^?1 of unionized ammonia resulted in 100% death of all larvae within 24 h. The tolerance of S. serrata larvae to total ammonia did not appear to increase with ontogenetic development. The results indicate that the concentrations at which total ammonia produces an acute or chronic response in mud crab larvae are far higher than those experienced in current larval production systems (0–0.5 mg L^?1 of total ammonia) used as industry standards in Australia.     

Effects of tank colour on larval survival and development of mud crab Scylla serrata (Forskål)

Hatchery culture of mud crabs has not yet achieved commercial viability despite decades of research efforts. Further research is therefore needed to better understand larval culture requirements of the crab. Based on anecdotal observations, an experiment was carried out to test whether the background colour of the culture vessel affected larval culture success. Newly hatched larvae of Scylla serrata were reared in culture vessels of five colours, i.e., black, dark green, maroon, sky blue and white. Larval survival and development were monitored daily until all of them either moulted to the first crab stage or died. The results showed clear effects of background colour on larval survival. A general tendency of higher larval survival in darker‐coloured backgrounds was evident. In particular, overall zoeal survival for larvae reared in black vessels was significantly higher than those reared in white ones. Background colour also appeared to affect larval development. Larvae reared in darker backgrounds generally had shorter development times and more synchronized moulting. A significant delay in zoeal development was observed in larvae reared in white vessels. Dark backgrounds possibly facilitated more efficient feeding, reduced settlement of larvae at the bottom of the vessels as well as minimized stress. This result appears to be the first to demonstrate that background colour can significantly affect larval survival and development of a crustacean species.     

INTERNATIONAL STUDY ON Artemia:1 XXI. INVESTIGATIONS INTO WHY SOME STRAINS OF Artemia ARE BETTER FOOD SOURCES THAN OTHERS. FURTHER NUTRITIONAL WORK WITH LARVAE OF THE MUD CRAB,Rhithropanopeus harrisii

In a series of studies conducted by members of the International Study on Artemia, differences in nutritional quality were documented between geographical strains of the brine shrimp Artemia. Concomitant with, and possibly related to nutritional effectiveness are differences in biometric traits and biochemical composition. Since these initial experiments could only hint at causal relationships, a series of experiments were carried out to further our understanding of cause and effect. In one experiment we tried to ascertain whether the factors responsible for poor survival in larvae fed some brine shrimp strains are cumulative throughout larval development or whether there are critical periods when larvae are more sensitive. Our results indicate that the factors contributing to poor growth and survival are cumulative. In a second experiment, we contaminated Brazil Artemia with diel-drin, chlordane and combinations of the two and fed them to mud crab (Rhithropanopeus harrisii) larvae. The levels of contamination were chosen to approximate those suspected of contributing to the poor food value of some brine shrimp strains. In this experiment, however, diel-drin and chlordane contamination appeared to have no effect on growth and survival of R. harrisii larvae. In a third experiment, we fed Utah strain Artemia on Isochrysis galbana for 24 hours and then fed these brine shrimp to mud crab zoeae. Previous work had shown that this regime made Utah Artemia more suitable as a food source for a prawn. However, in our experiments, it did not improve survival of R. harrisii.     

Improvement of larval rearing technique for mass seed production of snow crab <Emphasis Type="Italic">Chionoecetes opilio</Emphasis>

Larval rearing experiments were conducted to examine the potential for mass seed production of the snow crab Chionoecetes opilio using a total of eight 20-kL tanks. Tanks were equipped with agitators, which move the water using a rectangular blade to prevent the zoeas sinking to the bottom of the tank. Larval rearing water was treated with sodium nifurstyrenate once a week to reduce the chance of larval infection by pathogenic bacteria. Zo eas were fed with rotifers and Artemia nauplii. A total of 122 830 megalops and 16 660 first-stage crabs were produced. Thus, the potential for mass seed production of snow crab was determined. Survival rates up to the megalopal stage were high in tanks with a feeding regime that fed rotifers to larvae through an entire zoeal stage. This study also describes the fatty acid composition of snow crab larvae. It revealed that the first zoeas had a high DHA content and DHA/EPA ratio, but these values significantly decreased in the second stage zoeas and megalops. Improving the DHA content and/or DHA/EPA ratio of larvae should be important in studies on mass seed production technology of the snow crab.     

青蟹的营养需求研究及其配合饲料研制

青蟹属（Scylla）有锯缘青蟹（Scylla serrata），拟穴青蟹（S．paramamosain），紫螯青蟹（S．tranquebarica）和榄绿青蟹（S．olivacea）等4个种。我国以拟穴青蟹占绝对优势，它有个体大、生长快、适应性强、肉味鲜美、营养丰富等特点，已成为具有重要经济价值的海水养殖蟹类之一。     

Effects of temperature and salinity on the survival and development of mud crab, Scylla serrata (Forsskål), larvae

The combined effects of temperature and salinity on larval survival and development of the mud crab, Scylla serrata, were investigated in the laboratory. Newly hatched larvae were reared under 20 °C temperature and salinity combinations (i.e. combinations of four temperatures 25, 28, 31, 34 °C with five salinities 15, 20, 25, 30, 35 g L⁻¹). The results showed that temperature and salinity as well as the interaction of the two parameters significantly affected the survival of zoeal larvae. Salinity at 15 g L⁻¹ resulted in no larval survival to the first crab stage, suggesting that the lower salinity tolerance limit for mud crab larvae lies somewhere between salinity 15 and 20 g L⁻¹. However, within the salinity range of 20–35 g L⁻¹, no significant effects on survival of zoeal larvae were detected (P>0.05). The combined effects of temperature and salinity on larval survival were also evident as at low salinities, both high and low temperature led to mass mortality of newly hatched larvae (e.g. 34 °C/15 g L⁻¹, 34 °C/20 g L⁻¹ and 25 °C/15 g L⁻¹ combinations). In contrast, the low temperature and high salinity combination of 25 °C/35 g L⁻¹ resulted in one of the highest survival to the megalopal stage. It was also shown that at optimal 28 °C, larvae could withstand broader salinity conditions. Temperature, salinity and their interaction also significantly affected larval development. At 34 °C, the mean larval development time to megalopa under different salinity conditions ranged from 13.5 to 18.5 days. It increased to between 20.6 and 22.6 days at 25 °C. The effects of salinity on larval development were demonstrated by the fact that for all the temperatures tested, the fastest mean development to megalopa was always recorded at the salinity of 25 g L⁻¹. However, a different trend of salinity effects was shown for megalopae as their duration consistently increased with an increase in salinity from 20 to 35 g L⁻¹. In summary, S. serrata larvae tolerate a broad range of salinity and temperature conditions. Rearing temperature 25–30 °C and salinity 20–35 g L⁻¹ generally result in reasonable survival. However, from an aquaculture point of view, a higher temperature range of 28–30 °C and a salinity range of 20–30 g L⁻¹ are recommended as it shortens the culture cycle.     

白斑综合征病毒(WSSV)在拟穴青蟹体内增殖的研究

拟穴青蟹(Scylla paramamosain)因肉质鲜美、生长快速而成为我国主要的海水养殖经济蟹类,但是随着养殖规模的不断扩大,病害问题也越发严重。本研究通过流行病学调查和定量PCR跟踪检测的方法,研究了拟穴青蟹对白斑综合征病毒(WSSV)的易感性和WSSV在拟穴青蟹体内的增殖情况。结果表明,拟穴青蟹是WSSV的自然宿主,自然携带率为8.47%。WSSV可通过口服途径感染拟穴青蟹,并在拟穴青蟹体内快速增殖,注射感染5 d后,病毒量达到感染1d时的1.1×109倍,当病毒累积到一定量后即可致死拟穴青蟹。研究表明,拟穴青蟹是WSSV的天然宿主,在虾蟹混养过程中可以通过摄食WSSV感染虾而带毒或发病,并因此成为WSSV传播媒介,从而对虾蟹混养条件下WSSV的防治效果产生重要影响。     

Larval survival,development and growth in the horsehair crab,Erimacrus isenbeckii,cultured under different photoperiod conditions

Larval sinking causes larval mass mortality during seed production in the horsehair crab, Erimacrus isenbeckii. Under normal light conditions, horsehair crab larvae generally show negative phototactic behaviour and sink in their rearing seawater. It has been proposed that culturing larvae in the dark may prevent larval sinking. Herein, we examined the effect of photoperiods on horsehair crab larval survival and development to facilitate the development of larval rearing techniques that prevent sinking. Newly hatched larvae were reared with Artemia to the first crab stage in 2‐L beakers under five photoperiods: 0L:24D, 6L:18D, 12L:12D, 18L:6D and 24L:0D. Larvae survived and molted to the first crab stage under all tested photoperiod conditions. The survival rate improved with increasing light period, whereas the developmental period for each larval stage decreased with increasing light period. Longer light periods increased the carapace length at the first crab stage. Our results suggest that larvae could be cultured to the first crab stage in large‐scale tanks under constant darkness. However, significantly improved larval performance under longer photoperiodic conditions indicates a need for developing alternative culture techniques to control larval behaviour in the seed production tank.     

利用cDNA-AFLP技术研究副溶血弧菌感染下拟穴青蟹的基因差异表达

研究以实验室分离自汕头牛田洋青蟹养殖区的副溶血弧菌感染的健康拟穴青蟹,利用cDNA-AFLP技术分析感染前后拟穴青蟹肝脏组织基因的转录表达差异,最终获得了23个差异片段,其中20个片段成功测序。BLAST分析表明,序列与已知功能基因具有同源性的有6个,其中5个经real-time PCR重新验证为上调表达,主要涉及参与能量代谢的精氨酸激酶(arginine kinase)和甘油醛3磷酸脱氢酶(glyceraldehyde-3-phosphate dehydrogenase)、磷酸烯醇丙酮酸羧激酶(phosphoenolpyruvate carboxykinase),以及参与转运过程的精氨酰tRNA合成酶(arginyl-tRNA synthetase),同时,还有直接参与免疫防御反应的凝乳状蛋白酶(chymotrypsin-like proteinase)。另外,8个差异片段与已知基因或序列无同源性。     

Studies on pathogenicity and prevalence of white spot syndrome virus in mud crab, Scylla serrata (Forskal), in Zhejiang Province, China

Mud crab, Scylla serrata (Forskal), is the most commercially important marine crab species in China. In recent years, serious diseases have occurred in major mud crab culture regions in SE China. PCR detection of white spot syndrome virus (WSSV) in diseased mud crabs collected from Zhejiang Province during 2006–2008 showed a prevalence of 34.82%. To study the pathogenicity of WSSV to mud crab, healthy mud crabs were injected intramuscularly with serial 10‐fold dilutions of a WSSV inoculum. The cumulative mortalities in groups challenged with 10^?1, 10^?2, 10^?3 and 10^?4 dilutions were 100%, 100%, 66.7% and 38.9% at 10 days post‐injection, respectively. All moribund and dead mud crabs except the control group were positive for WSSV by PCR. Based on the viral load of the WSSV inoculum by quantitative real‐time PCR, the median lethal dose (LD50) of WSSV in S. serrata was calculated as 1.10 × 10⁶ virus copies/crab, or 7.34 × 10³ virus copies g^?1 crab weight. The phenoloxidase, peroxidase and superoxide dismutase activities in haemolymph of WSSV‐infected moribund crabs, were significantly lower than the control group, whereas alkaline phosphatase, glutamate‐pyruvate transaminase and glutamic‐oxaloacetic transaminase were higher than in the control group. WSSV was mainly distributed in gills, subcuticular epithelia, heart, intestine and stomach as shown by immunohistochemical analysis with Mabs against WSSV. The epithelial cells of infected gill showed hypertrophied nuclei with basophilic inclusions. Numerous bacilliform virus particles were observed in nuclei of infected gill cells by transmission electron microscopy. It is concluded that WSSV is a major pathogen of mud crab with high pathogenicity.     

拟穴青蟹不同发育时期胚胎基因表达的内参基因的筛选

为获得适用于研究拟穴青蟹(Scylla paramamosain)不同发育时期胚胎基因表达的内参基因,本研究采用3个内参基因筛选软件geNorm、NormFinder及BestKeeper对微管蛋白α1A(Tuba1a)、核糖体蛋白L13(Rpl13)、泛素(UBQ)、核糖体蛋白S6激酶(Rps6)、精氨酸激酶(Ak)、3-磷酸甘油脱氢酶(gapdh)、28S核糖体RNA(28S)、18S核糖体RNA(18S)和延伸因子1A基因(EF-1α)等9个常用候选内参基因在拟穴青蟹不同发育时期胚胎的表达稳定性进行分析。geNorm分析表明, EF-1α和Rpl13的表达稳定性最高,并且采用2个内参基因同时校正目标基因的定量结果可以达到最优效果; NormFinder分析表明, gapdh和EF-1α是9个候选内参基因中表达最稳定的; BestKeeper分析表明,gapdh的标准偏差和变异系数是9个候选基因中最低的。综合3个内参基因筛选软件,可以选用EF-1α,或选用EF-1α和gapdh双内参同时校正拟穴青蟹不同胚胎发育时期各基因的表达情况。     

Quality assessment of newly hatched mud crab,Scylla serrata,larvae

Starvation and exposure to formalin were investigated as possible stress tests for evaluating the quality of mud crab, Scylla serrata, larvae. For the starvation stress test, newly hatched zoeae stocked in 150‐ml containers were either starved or fed rotifers. Similarly, newly hatched zoeae were stocked in containers with seawater of 0 (control), 20, 30 and 40 mg/L formalin for the formalin stress test. The zoeae from the same batches were used for seed production to monitor their performance and validate the results of stress tests. Starvation was found to be unsuitable for larval quality evaluation. However, the impact of initial food deprivation on the newly hatched larvae indicates that feeding immediately after hatching is necessary for mud crab larvae. Exposure of larvae to 40 mg/L formalin for 3 hr appeared to be a reliable and practical method for larval quality assessment as the survival of larvae in the mass production tanks validated the classification of good and poor quality batches in the stress tests. On this basis, a hatchery operator can decide which batch should be cultured further. Finally, there appears to be a link between the quality of larvae and the performance at the megalopa and early juvenile crabs.     

Characterization of Aquimarina hainanensis isolated from diseased mud crab Scylla serrata larvae in a hatchery

Mass mortality due to necrosis signs occurred in hatchery-reared zoea stage larvae of the mud crab Scylla serrata in Okinawa, Japan, and a causative bacterium was isolated. In this study, we identified and characterized the bacterium by genome analysis, biochemical properties and pathogenicity. The bacterium was a Gram-negative, non-motile, long rod, forming yellow colonies on a marine agar plate. It grew at 20–33°C (not at 37°C) and degraded chitin and gelatin. Phylogenetic analysis of the 16S rRNA gene sequence identified the bacterium as Aquimarina hainanensis. Genome sequence data obtained from Illumina MiSeq generated 29 contigs with 3.56 Mbp in total length and a G + C content of 32.5%. The predicted 16 chitinase genes, as putative virulence factors, had certain homologies with those of genus Aquimarina. Experimental infection with the bacterium conducted on larvae of four crustacean species, brine shrimp Artemia franciscana, freshwater shrimp Caridina multidentata, swimming crab Portunus trituberculatus and mud crab S. serrata, revealed that this bacterium was highly virulent to these species. The present study suggests that the bacterium caused mass mortality in mud crab seed production was A. hainanensis and can be widely pathogenic to crustaceans.     

Effects of Starvation and Feeding on Lipid Class and Fatty Acid Profile of Late Stage Mud Crab,Scylla serrata,larvae

Lipid class and fatty acid (FA) analysis were conducted on newly molted, fed, and starved zoea V and megalopa of the mud crab, Scylla serrata (S. serrata). Larvae starved for 4 d showed a substantial decrease in total FA content, from 49.67 μg/mg to 13.94 μg/mg ash‐free dry weight (AFDW) at the zoea V stage, and from 38.47 μg/mg to 10.40 μg/mg AFDW at the megalopa stage. This depletion indicates that S. serrata larvae effectively utilize stored lipid reserves for energy during periods of food deprivation. Megalopa subjected to longer starvation periods, however, did not utilize lipid as the major energy source after day 4, suggesting increased reliance on protein catabolism during prolonged starvation. At both larvae stages the major FAs were 18:1n‐9, 16:0, 20:5n‐3 (eicosapentaenoic acids, EPA), 18:3n‐3 (linolenic acid, LNA), 18:0 and 22:6n‐3 (docosahexaenoic acid, DHA) and this FA profile persisted in both fed and starved larvae. The highly unsaturated fatty acids (HUFA), EPA, DHA, and arachidonic acid (20:4n‐6, AA) were not conserved in tissue during starvation, indicating that HUFA requirements might be lower for S. serrata larvae than shown for other crustaceans. Similarly, a high level of LNA in newly molted zoea V and megalopa were rapidly depleted in unfed larvae, indicating that this FA had an important role as an energy reserve. Throughout the study, FAs from the polar lipid fraction dominated larvae tissues, while FAs from the neutral lipid constituted the largest accessible energy reserve during starvation (depleted from 23.05 to 1.23 μg/mg AFDW in zoea V, and from 19.00 to 1.27 μg/mg AFDW in megalopa). The results of this study provide new insight into lipid utilization of S. serrata larvae during development, an important step toward development of formulated diets for use in mud crab hatcheries.     

The effects of supplemental dietary cholesterol on growth, development and survival of mud crab, Scylla serrata, megalopa fed semi-purified diets

The effects of varying levels of dietary cholesterol on growth, development time and survival of mud crab, Scylla serrata megalopa were investigated using semi-purified microbound diets (MBD). Five iso-energetic diets containing different level of cholesterol ranging from 0.14% to 1% of dry weight of the diet were tested. Fifteen megalopa were reared individually for each dietary treatment, and development time and survival were recorded on a daily basis. More than 25% of megalopa from all treatments were able to metamorphose into the first crab stage, suggesting that the endogenous level of cholesterol in the basal diet (0.14%) was sufficient to support development of the megalopa stage of this species. Widest mean carapace width (3.53 ± 0.08 mm) and highest mean dry weight (2.11 ± 0.22 mg) were recorded for juveniles that molted from megalopa fed live Artemia, whereas no megalopa in the unfed control treatment metamorphosed into crabs. The average development time from megalopa to the juvenile crab stage varied between the treatments, where megalopa fed live Artemia or MBD containing 0.2%, 0.4% or 0.8% total cholesterol showed the most synchronized molting (between 8.0 and 9.9 days). Longest development time was recorded for the megalopa fed diets containing 0.14% or 1% total cholesterol (both 11 days). Highest survival (74.3%) was recorded for the megalopa fed a diet containing 0.8% cholesterol. The results of this study are valuable in research to develop formulated diets for mud crab larvae as a replacement for live food in hatchery culture.     

Evaluation of limb autotomy as a promising strategy to improve production performances of mud crab (Scylla olivacea) in the soft‐shell farming system

Soft‐shell crab, a newly moulted crab having non‐calcified and hydrated soft exoskeleton, farming has been increasing tremendously in recent years throughout the world due to its high market price and consumer preferences. However, high aggressiveness and cannibalistic behaviour of mud crab limit its culture to an individual chamber system which ultimately makes the soft‐shell mud crab farming space and labour‐intensive. Therefore, the aim of this study was to improve the efficiency of soft‐shell crab production by autotomy of the claw and/or walking legs to reduce the moulting duration and intensify the culture system through double stocking in the existing individual chamber culture system. To achieve our objectives, a series of experiment were conducted at both indoor and on‐farm levels by removing the claw and/or walking legs of Scylla olivacea for two consecutive moulting cycles. Results showed that both claw ablation significantly (p < .01) shortened the moulting duration and increased the carapace width, weight gain, specific growth rate, feeding efficiency and yield parameter compared to the non‐ablated crabs more prominently at 1st moulting than the 2nd moulting in both indoor and on‐farm trials. Ablation of all walking legs while keeping the claw intact did not significantly influence (p > .05) the moulting duration and carapace width, but significantly (p < .01) improved the specific growth rate, weight gain, feeding efficiency and yield parameters at 1st moulting compared to the non‐ablation and unilateral three walking leg ablation groups. However, ablation of all appendages (both claw and walking legs) showed significant (p < .01) improvements of carapace width, weight gain, specific growth rate, feeding efficiency and yield parameters, and shortened the moulting duration up to 23 days from 34 days during 1st moulting and up to 27 days from 40 days at 2nd moulting. The survivals of different autotomized mud crabs were statistically non‐significant (p > .05) to the non‐autotomized crabs in various indoor and on‐farm trials. Besides improving the production performances, ablation of bilateral claw and all appendages allowed to double the stocking density in the existing individual chamber‐based soft‐shell crab farming that enhanced the production about threefold higher than the existing individual chamber‐based culture system. Finally, our results suggest that autotomy could be a promising technology for the commercial farming of soft‐shell mud crab in near future.     

The effect of poly‐β‐hydroxybutyrate on the performance of Chinese mitten crab (Eriocheir sinensis Milne‐Edwards) zoea larvae

Two experiments were conducted regarding the effect of poly‐β‐hydroxybutyrate (PHB) on the survival and development of Chinese mitten crab (Eriocheir sinensis Milne‐Edwards) larvae. Different PHB delivery approaches (particulate, enriched in filter feeding prey, or a combination of both) and feeding levels were applied to crab larvae from the zoea 2 (Z2) up to the megalopa stage. Bio‐encapsulation into rotifers and Artemia at a PHB dose of 100 mg L^?1 seemed an efficient approach to deliver PHB to the larvae and resulted in a significantly enhanced survival, development rate and osmotic tolerance. The results indicate that PHB should only be applied as a feed additive rather than as a food source, and that the availability of an adequate amount of nutrients seems to be of major importance for the PHB to induce these beneficial effects.     

Optimal first feed organism for South African mud crab <Emphasis Type="Italic">Scylla serrata</Emphasis> (Forskål) larvae

It is not known whether rotifers or Artemia nauplii are the best first food for South African mud crab Scylla serrata larvae. In order to test this, larvae were fed with five different test diets. These were rotifers for the first 8 days and newly hatched EG^® type Artemia nauplii (San Francisco Bay) from day 6 onwards (treatment R6A); newly hatched EG^® type Artemia nauplii throughout the rearing period (treatment EG); newly hatched Vinh-Chau strain (Vietnam) Artemia nauplii throughout the rearing period (treatment VC); decapsulated cysts of EG^® type Artemia throughout the rearing period (treatment DECAP); or decapsulated cysts supplemented with low densities of Artemia EG type Artemia nauplii (treatment MIX). Two experiments were conducted approximately 1 month apart using larvae from two different female crabs. Although results showed it is possible to rear S. serrata larvae through metamorphosis on Artemia nauplii exclusively, larval performance (development, survival and successful metamorphosis) was enhanced by the inclusion of rotifers as a first feed.No significant difference in performance was recorded between larvae fed on the two strains of Artemia nauplii. Larvae fed on decapsulated cysts in treatments DECAP and MIX performed poorly, but there were indications that decapsulated cysts and other inert diets may have potential as supplements to live food in the rearing of S. serrata larvae.     

Long‐term trends and drivers of larval phenology and abundance of dominant brachyuran crabs in the Gulf of St. Lawrence (Canada)

Climate change has led to major shifts in the timing of biological events, with many studies demonstrating earlier phenology in response to warming. However, few of these studies have investigated the effects of climate change on the phenology of larvae in marine species. Phenological shifts can result in mismatches between consumers and prey and hence affect growth and survival of individuals, and ultimately population demography. We investigated the temporal changes in phenology and abundance of the larvae of dominant brachyuran crabs in the southern Gulf of St. Lawrence (eastern Canada) based on plankton collections spanning 1982–2012. The Gulf of St. Lawrence has warmed since the early 1990s, and our analyses revealed that larvae of snow crab (Chionoecetes opilio) and toad crabs (Hyas spp.) exhibited a significant trend towards earlier phenology over the 30‐year study period. This shift in phenology appeared to be a consequence of the effect of climate warming on both the timing of hatching and larval development rate. Larval abundance responded differently by crab taxon to climate warming, likely due to differences in thermal tolerance. The warming trend was unfavourable to snow crab, which is the most cold‐adapted and stenothermic of the taxa examined in this study. The abundance of snow crab larvae was lower when sea ice retreat occurred earlier than day 110 of the year and sea surface temperature was higher than 8.5°C. On the other hand, larval abundance of rock crab (Cancer irroratus), which prefers higher temperatures, was positively related to surface temperature.