FINAL REPORT COVER SHEET

Transcription

1 FINAL REPORT COVER SHEET 3 April 211 Final Report to: The Barnegat Bay Partnership Project Title: Assessing population structure, reproductive potential and movement of adult blue crabs in Barnegat Bay Submitted by: Paul R. Jivoff Associate Professor Department of Biology Rider University 283 Lawrenceville Rd Lawrenceville, NJ 8648 TEL: FAX: pjivoff@rider.edu

2 Background and Justification Blue crabs are one of the most important commercial and recreational fisheries in New Jersey (Kennish et al. 184; Stehlik et al. 18) and throughout the mid-atlantic region (Jordan 18). Over the past three decades, blue crab populations in other mid-atlantic estuaries (e.g., Chesapeake Bay and Delaware Bay) have declined drastically (Abbe and Stagg 16; Cole 18; Uphoff 18). These reductions may stem from a number of factors including loss or degradation of habitat for recruits and juveniles (Lipcius et al. 25), reduced water quality (Mistiaen et al. 23), and significant natural and fishing mortality (Lipcius and Stockhausen 22). Over the past decade in the mid-atlantic region, as crab catches continue to decline in Delaware Bay, the relative importance of New Jersey blue crab populations has increased -fold in terms of both commercial landings and economic value (NOAA fisheries data). Some of this increase stems from New Jersey estuaries other than Delaware Bay. For example, in the past decade, Barnegat Bay s percentage of New Jersey s blue crab catch has quadrupled (NJDEP fisheries data; Figure 1). As the relative importance of blue crab populations in estuaries like Barnegat Bay increases, the extent of fishing effort and the potential for user conflicts may also increase. Therefore it is critical to gather information about the population status and the extent of fishing effort (commercial and recreational) on blue crab populations in estuaries like Barnegat Bay. Indeed, as indicated in the BBNEP Monitoring Program Plan (MPP): an assessment of the seasonal availability and habitat use patterns associated with finfish and blue crab resources should be conducted for Barnegat Bay. Objectives The objectives of this study were to examine the relative abundance and population structure (e.g., size structure, sex ratio) of adult blue crabs in Barnegat Bay using field sampling with traps and otter trawl. I also measured temporal and spatial variation in aspects of the reproductive potential (e.g., sperm stores of both sexes, brood production of field-caught females) and movement patterns of adult crabs (with mark-recapture data). Mark-recapture data and direct counts of commercial crab traps (in selected locations) also provide information on the temporal and spatial extent of fishing effort (commercial and recreational) on adult blue crabs in the Bay. Methodology Field Sampling: I examined adult blue crab population structure (abundance, size composition, sex ratio) using baited traps sampled daily for four consecutive days, every other week from June-August and 2

3 sampling one day every other week in September. Sampling via otter trawl also occurred twice per month (June-August) at the same sampling areas as trapping (see below), but not simultaneously with trapping, and after at least seven consecutive days without trapping. Trawling occurred at a constant speed (2,5 rpm) for two minutes using a 4. m otter trawl with 6 mm cod end mesh. Barnegat Bay was divided into seven approximately equal sized areas (each ~8km long; see Figure 2) and four sampling sites in each area were established using GPS. Each sampling day, four traps were randomly assigned to one of the four sites in each area (and placed at least 5m apart from one another). Crabs were separated by trap or trawl haul, returned to the Rutgers University Marine Field Station, and measured for carapace width, age, sex, sexual maturity, molt stage, limb loss and regeneration, and ovigerous stage (adult females). Sexual maturity and molt stage were determined using previously established methods (Jivoff 17b). Crabs from these collections were also used for measurements of reproductive potential (see below). Physical characteristics near the first and last trap in each site including depth, salinity, temperature, and dissolved oxygen were taken with a hand-held YSI datalogger. In selected areas (e.g., those where commercial fishermen used individual surface buoys to mark each trap), on each sampling day, I counted the number of commercial crab traps seen in-route from the current sampling site to the next day s site. Reproductive Potential Studies: A weekly sample of crabs from five size categories of each sex from each area were frozen for subsequent dissection and measurement of reproductive potential: sperm stores and seminal fluid weight in males; sperm stores, ovarian weight and developmental stage, and brood stage in females using previously established techniques (Jivoff 17b; Hines et al. 23). Mark-Recapture Studies: Each month, a sample of crabs of each sex was tagged and released from one site in each area. The tags were plastic Floy tags affixed to the carapace using malleable stainless steel wire wound around the lateral spines (Aguilar et al. 25). Information imprinted on the labels included BBNEP, contact phone number, individual tag number and requested the recording of the following data: tag number, capture date, capture location (GIS coordinates if known), capture depth, and capture gear. Captors submitted this information via phone or via my internet blog site (njbluecrabs.wordpress.com). Results Physical Characteristics 3

4 Temperature varied by month (F 4,441 =44., P<.1), decreasing from July through September, however not by sampling area (F 6,441 =., P=.8) (Figure 3A). As expected, salinity varied by month (F 4,441 =4.6, P=.31), peaking in July or August, and by sampling area (F 6,441 =36.68, P<.1), with a gradient of decreasing salinity between areas 4 and 7 (Figure 3B). Dissolved oxygen varied by month (F 4,441 =62.1, P<.1), with values dropping between June and July followed by a steady increase through September, however not by sampling area (F 6,441 =1.3, P=.217) (Figure 3C). Depth did not vary by month (F 4,441 =1.78, P=.132), but did vary by sampling area (F 6,441 =24.8, P<.1), primarily because areas 2 and 3 were relatively shallow but the absolute differences were.5m or less (Figure 3D). Adult Population Structure Abundance A total of 5,56 blue crabs were captured in traps over the course of this study; 3,84 adult males, 1,154 adult females, 155 juvenile males, and 3 pre-pubertal females. The predominance of adult males in our study (3.3 times that of females) is consistent with that of the commercial blue crab fishery in Barnegat Bay during the summer months which, since 2, has caught between 3 and 8 times as many males as females (NJ DEP data). I will report the abundance of crabs as catch per unit effort (CPUE) because the number of crabs caught was not always based on four traps per site (e.g., due to missing or lost traps between sampling days). Overall, male abundance was greater than that of females (F 1,281 =5.87, P<.1). Male abundance exceeded that of females at every sampling area except for area 4 (sex x area interaction; F 6,281 =6.88, P<.1) (Figure 4), the area closest to Barnegat Inlet which adult females use for spawning (see below). Male abundance exceeded that of females in each month (sex x month interaction; F 4,281 =7.1, P<.1). Because of the prevalence of males, a more in-depth analysis of the temporal and spatial variation in the abundance of males will follow. Male abundance varied significantly among the months (F 4,128 =15.57, P<.1), with fewer males in June and October as compared to July and August, but not among the sampling areas. However, the sampling areas did not exhibit the same monthly pattern in male abundance (area x month interaction (F 24,128 =2.41, P=.8). In areas 1, 4 and 5, the abundance of males was lower in June compared to August (area 1) or both July and August (areas 4 and 5) (Figure 5). In June, male abundance in area 7 was greater than areas 1, 4, 5, and 6 (Figure 5). In July, male abundance in areas 7 and 5 was greater than areas 1 and 2 and male 4

5 abundance in area 6 was greater than area 2 (Figure 5). The temporal and spatial variation in the relative abundance of both sexes created temporal and spatial variation in the sex ratio (# of males : # of females) (see below). Sex Ratio The sex ratio varied both temporally (F 4,15 =3.42, P=.1), with July having a larger M:F ratio than June and August, and spatially (F 6,15 =4.6, P=.3), with sampling area 7 having larger M:F ratio than areas 2, 3, and 4 (Figure 6). The spatial variation in sex ratio exhibits the greatest change between areas 4 and 7 (see Figure 6), which also represents the largest change in salinity among the areas (see Figure 3B). There is a significant negative relationship between average salinity and average M:F ratio among areas 4 and 7 (Y= X ) with salinity explaining 8% of the variation in sex ratio. Both female (F 3,84 =.87, P<.1) and male abundance (F 3,84 =5.38, P=.2) vary among these sampling areas, with female abundance decreasing and that of males increasing, indicating sex ratio variation during the summer months, is regulated by the abundance of both sexes and moderated by salinity. Size Male size varied significantly by sampling area (F 6,3658 =2.55, P=.18), with male size in area 3 being less than in areas 5 and 6, and by month (F 4,3658 =42., P<.1), with male size increasing from June to July then falling monthly until September. Male size in June and/or July was significantly greater than August and/or September in areas 1-5 (Figure 7). In area 7 that trend was reversed; male size in June was significantly less than July, August and September (Figure 7). The size of adult females alone did not vary significantly by sampling area (F 6,18 =1.84, P=.88) but did vary by month (F 4,18 =5.16, P=.4) with female size in June, July, and August being larger than October. When both adult females and pre-pubertal females were included in the analysis, female size varied temporally (F 3,144 =35.5, P<.1) and spatially (F 6,144 =15.21, P<.1), with female size typically being smaller in August than in June and July (Figure 8). This pattern in female size was dependent upon the relative percentage of pre-pubertal females in the population (i.e., reducing the average female size) which increased monthly from June to August, peaking in August. Monthly female size decreased as the percentage of prepubertal females in the population increased (Y=-38.X ) and the percentage of pre-pubertal females 5

6 explained 67% of the variation in monthly female size. Similarly, female size among the sampling areas decreased as the percentage of pre-pubertal females increased in the population (Y=-38.64X ) and the percentage of pre-pubertal females explained 8% of this spatial variation in female size. Reproductive Potential Female Brood Production The largest numbers of ovigerous females were concentrated closest to the two inlets in Barnegat Bay; Little Egg Inlet near Tuckerton and Barnegat Inlet near Waretown (Figure ). The abundance of ovigerous females and the developmental stages of their eggs varied temporally (Figure ), indicating that the spawning season began in May (there were already females with late stage broods captured in early June) and ended in August (no ovigerous females were captured in September or October). As the summer progresses, there appears to be an increasing percentage of females carrying mid stage broods with a concomitant decrease in the percentage of females carrying mid-late and late stage broods suggesting a certain degree of synchrony in brood production among adult females. Female Sperm Stores The seminal receptacles (i.e., sperm storage organs) and ovaries from females of 6 size categories were extracted and weighed separately. The weight of seminal receptacles from females showing signs of recent mating (i.e., early stage ovaries) did not vary significantly by month (F 3,7 =1.26, P=.25) or female size (F 1,7 =.846, P=.361) but did vary significantly by sampling area (F 6,7 =2., P=.11), with weights in area 7 being greater than areas 4 and 6 (Figure 11). This spatial variation in female sperm and seminal fluid stores may be positively associated with the spatial availability of males; the sex ratio in area 7 was significantly greater than area 4 (see Figure 6). Male Sperm Stores The spermatophore and seminal fluid sections of the vas deferentia were extracted from males of 6 size categories and weighed separately. The weight of the spermatophore (F 6,646 =5.57, P<.1) and seminal fluid (F 6,646 =4.1, P=.1) components varied significantly by area. The weight of the spermatophore (F 3,646 =3.7, P=.27) and seminal fluid (F 3,646 =7.27, P=.1) components varied significantly by month. The weight of the spermatophore (F 5,646 =36.81, P<.1) and seminal fluid (F 5,646 =4.46, P<.1) components varied 6

7 significantly by male size category, with both components getting heavier with increasing male size class (Figure 12). The weight of both the spermatophore and seminal fluid sections of male size class 1, 2 and 3 were significantly less than size classes 4, 5, and 6. These results suggest that male reproductive potential increases with male size such that large males have the capacity to provide females with greater amounts of both sperm and seminal fluid. Movement During the course of the study, 1,173 crabs were tagged and released (77 males, 43 females) and 87 were recaptured (7.4% recapture rate), which is slightly lower than recapture rates of other tag-recapture studies performed on blue crabs (Aguilar et al. 25) as well as last year s recapture rate (%). Of the recaptured crabs, the majority (83%) were males. More recaptures were reported by commercial fishermen (56%) than by recreational fishermen (44%). This represents a slight reversal from last year s study (commercial recaptures=48%, recreational recaptures=52%) but very different from other blue crab tagging studies which typically report the overwhelming majority of recaptures from commercial fishermen (Aguilar et al. 25). There was considerable variation in the distance traveled by tagged crabs but for at least the first 4 days, crabs tended to travel farther the longer they were at large (Figure 13). The sampling areas are approximately 7km long and, on average, most recaptured crabs remained in the same sampling area in which they were tagged however, some crossed sampling area boundaries with the longest distance traveled being approximately 25 km by a crab at large for 4 days (Figure 13). It took longer to recapture most of the tagged crabs as compared to last year s study: after 14 days 6% of the tagged crabs were recaptured (Figure 13), as compared to last year when it took only 5 days to recapture 6% of the tagged crabs. In other blue crab tagging studies, 2 days were required to recapture a similar percentage of tagged crabs (Aguilar et al. 25). The recapture results suggest that fishing in Barnegat Bay may be relatively intense and that both commercial and recreational fishing represent important sources of fishing mortality. Summary and Conclusion Current Year: 2 In 2, there was considerable temporal and spatial variation in various aspects of adult blue crab population structure in Barnegat Bay including the abundance and size of both sexes and sex ratio. These 7

8 aspects of population structure influence the reproductive biology of blue crabs as seen in temporal and spatial patterns in different measures of the reproductive potential of both sexes. For example, the availability of males, especially large males with greater sperm stores, may influence female reproductive potential by regulating the supply of sperm and seminal fluid females obtain for brood production. Comparison of 28 and 2 Many aspects of the adult blue crab population, as well as the environmental variables that may influence blue crabs, were consistent during the two years of this study. The temporal (monthly) and spatial (among sampling areas) variation in physical variables (temperature, salinity, dissolved oxygen and depth) was similar between the years. Most notable because of its potential effects on blue crab population structure was salinity. In each year, a salinity gradient (ranging from 6- ppt, depending on the month) occurred between sampling areas 4 (Waretown) and 7 (Cedar Grove). This gradient is not as strong as in flooded-river estuaries such as Delaware Bay or Chesapeake Bay, however its effect on the relative abundance of males and females, and thus the sex ratio, is consistent with flooded-river estuaries (Hines et al. 187; Jivoff and Able 23). With decreasing salinity, the abundance of males increases whereas the abundance of females decreases, creating very male-biased sex ratios in lower salinity areas. Sex ratio influences various aspects of the blue crab mating system including the degree of sexual competition among males (Jivoff 17a; Jivoff 17b) and the sexual behavior of both males and females (Jivoff and Hines 18b; Jivoff and Hines 18a) which may influence the mating success and potentially the reproductive output of both sexes. Overall, the total number of crabs captured, the sexual composition of the adult population, as well as the temporal and spatial variation in the abundance and size of crabs were very consistent between the two years of this study. In each year, approximately 5, crabs were captured with a male:female ratio of 3:1. Males were consistently more abundant than females in each month and at each sampling area, except area 4 (Waretown). Waretown is the area closest to Barnegat Inlet where, as suggested by blue crab spawning behavior in other estuaries (McConaugha et al. 183; Epifanio et al. 184; Tankersley et al. 18; Dickinson et al. 26), adult female blue crabs would be expected to release their larvae. As a result, in each year most ovigerous females were captured in areas 1 (near Little Egg Inlet) and 4 (near Barnegat Inlet). 8

9 The temporal and spatial variation in the abundance and size of males were of particular interest because males represent a significant proportion of the summer trap fishery which represents a large proportion of the total annual blue crab harvest. Again, the patterns of temporal and spatial variation in the abundance and size of males between the years was quite consistent. In general, male abundance and size peaked in July or August both of which may be related to high incidences of molting during or immediately prior to those times thus suggesting a summer growing season. The concurrent increases in male size and abundance also suggest that many of the adult males (i.e., year 1+ males ) available in late spring-early summer molt to become the largest males in the population by July or August. Similarly, those juvenile males (i.e., year 1 males ) available in late spring-early summer molt to become the relatively small adults present towards the end of the summer. These two cohorts of males represent the bulk of the harvestable population of males during the summer and this population is essentially determined by the availability of those males present in late May and June. This suggests that factors influencing recruitment and overwintering survival are important for understanding the harvestable population. There was not a consistent pattern between the years in adult female size. However, in both years when adult and pre-pubertal females were considered together, the percentage of pre-pubertal females (females immediately prior to the terminal molt to maturity, their sole opportunity to mate) in the population had a significant influence on the temporal pattern of female size: when the percentage of pre-pubertal females was high (typically in August), average female size decreased. Pre-pubertal females represent those females in the population that are sexually receptive. Therefore the relative abundance of pre-pubertal females influences the degree of sexual competition among males in the population, affecting the sexual behavior of both males and females (Jivoff and Hines 18b; Jivoff and Hines 18a) and influencing the mating success and potentially the reproductive output of both sexes. Most female blue crabs mate once in their life acquiring seminal fluid and the sperm they will use to fertilize their lifetime supply of eggs, therefore factors that influence the sperm stores of females can influence female reproductive output. One factor that was not consistent between the years of the study was female sperm stores. Considering only those females showing signs of recent mating, monthly variation was observed in 28 whereas spatial variation was seen in 2. In both cases, the variation may be associated with access to relatively large males,

10 since in both years of this study and in previous studies (Jivoff 17b; Carver et al. 25) large males had greater stores of sperm and seminal fluid. The variation in female sperm stores may also be associated with male-biased sex ratios because, in response to increased sexual competition, males pass larger amounts of sperm and seminal fluid to females (Jivoff 17a; Jivoff 17b). The amount of sperm females have stored influences brood production (Hines et al. 23) and during this study there was considerable variation in the abundance of ovigerous females as well as the timing of brood production and the developmental stage of broods. Some of this variation could be explained by individual females producing multiple broods during the summer, however we have no information on the factors that influence the number of broods female blue crabs in New Jersey can produce during a season or during their lifetime. This lack of information prompted the study performed in 2 specifically examining factors that influence female brood production.

11 Pounds Caught Barnegat Bay % Delaware New Jersey Barnegat Bay % Barnegat Bay Year Figure 1. Annual summer-time (June-August) catch (in pounds) of blue crabs in Delaware, New Jersey, and Barnegat Bay (left Y axis) and the percentage of the total New Jersey summer-time catch represented by Barnegat Bay (right Y axis). Data from NOAA and NJDEP Figure 2. Map of Barnegat Bay showing locations of seven equal sized sampling areas for this study. 11

12 Temperature (oc) Salinity (ppt) Depth (m) Dissolved Oxygen (mg/l) Tuckerton West Creek Manahawkin Waretown Forked River Bayville Sampling Area A B C D Cedar Grove Figure 3. Monthly (+ 1SE) physical characteristics of the sampling areas including temperature (A), salinity (B), dissolved oxygen (C), and depth (D). Towns nearest to the sampling areas are included on the X axis. 12

13 Catch per Unit Effort Tuckerton West Creek Manahawkin Waretown Forked River Bayville Cedar Grove Sampling Area Figure 4. Catch per unit effort (+ 1SE) of males and females in each sampling area, June- September 2. Towns nearest to the sampling areas are included on the X axis. 12 Females Males Catch per Unit Effort Month Tuckerton West Creek Manahawkin Waretown Forked River Bayville Sampling Area Figure 5. Monthly catch per unit effort (+ 1SE) of males in each sampling area, June- September 2. Towns nearest to the sampling areas are included on the X axis. 13 Cedar Grove

14 M:F Ratio Tuckerton West Creek Manahawkin Waretown Forked River Bayville Cedar Grove Sampling Area Figure 6. Male:Female ratio (+ 1SE) in each sampling area. Towns nearest to the sampling areas are included on the X axis Width (mm) Month Tuckerton West Creek Manahawkin Waretown Forked River Bayville Cedar Grove Sampling Area Figure 7. Monthly male size (+ 1SE) in each sampling area. Towns nearest to the sampling areas are included on the X axis. 14

15 15 14 Width (mm) Month 6 78 Tuckerton West Creek Manahawkin Waretown Forked River Bayville Cedar Grove Sampling Area Figure 8. Monthly female size (+ 1SE) in each sampling area. Towns nearest to the sampling areas are included on the X axis Percent Ovigerous Females Non-ovigerous Ovigerous Tuckerton West Creek Manahawkin Waretown Forked River Bayville Sampling Area Cedar Grove Figure. The percentage of ovigerous and non-ovigerous females in each sampling area, June- September 2. Numbers inside bars represent sample size of all adult females captured at the area. Towns nearest to the sampling areas are included on the X axis. 15

16 Percent Egg Stage late mid-late mid early June July August Sampling Week Figure. The weekly percentage of ovigerous females with different egg developmental stages females in each sampling area. Numbers inside bars represent sample size of ovigerous females. The months for each sampling week are included on the X axis. 4.5 Seminal Receptacle Weight (g) Tuckerton West Creek Manahawkin Waretown Forked River Bayville 16 Cedar Grove Sampling Area Figure 11. Weight (+ 1SE) of female seminal receptacles in each sampling area. Towns nearest to the sampling areas are included on the X axis.

17 Weight of Component (g) Spermatophores Seminal Fluid Cumulative Percentage >15 Size Class (mm) Figure 12. Weight (+ 1SE) of the spermatophore and seminal fluid components in the vas deferentia of males from 6 size categories, June-October Cumulative Percentage Distance Traveled >15 Days at Large Figure 13. Cumulative percentage and distance (+1 SD) traveled of recaptured crabs during the number of days they were at large, June-August Distance Moved (km)

18 Bibliography Abbe GR, Stagg C (16) Trends in blue crab (Callinectes sapidus Rathbun) catches near Calvert Cliffs, Maryland, from 168 to 15 and their relationship to the Maryland commercial fishery. Journal of Shellfish Research 15: Aguilar R, Hines AH, Wolcott TG, Wolcott DL, Kramer MA, Lipcius RN (25) The timing and route of movement and migration of post-copulatory female blue crabs, Callinectes sapidus Rathbun, from the upper Chesapeake Bay. Journal of Experimental Marine Biology and Ecology 31: Carver AM, Wolcott TG, Wolcott DL, Hines AH (25) Unnatural selection: Effects of a malefocused size-selective fishery on reproductive potential of a blue crab population. Journal of Experimental Marine Biology and Ecology 31: 2-41 Cole RW (18) Changes in harvest patterns and assessment of possible long-term impacts on yield in the Delaware commercial blue crab fishery. Journal of Shellfish Research 17: Dickinson GH, Rittschof D, Latanich C (26) Spawning biology of the blue crab, Callinectes sapidus, in North Carolina. Bulletin of Marine Science 7: Epifanio CE, Valenti CC, Pembroke AE (184) Dispersal and recruitment of blue crab larvae in Delaware Bay, U.S.A. Estuarine, Coastal and Shelf Science 18: 1-12 Hines AH, Jivoff PR, Bushmann PJ, van Montfrans J, Reed SA, Wolcott DL, Wolcott TG (23) Evidence for sperm limitation in the blue crab, Callinectes sapidus. Bulletin of Marine Science 72: Hines AH, Lipcius RN, Haddon AM (187) Population dynamics and habitat partitioning by size, sex, and molt stage of blue crabs Callinectes sapidus in a subestuary of central Chesapeake Bay. Marine Ecology Progress Series 36: Jivoff P (17a) The relative roles of predation and sperm competition on the duration of the postcopulatory association between the sexes in the blue crab, Callinectes sapidus. Behavioral Ecology and Sociobiology 4: Jivoff P (17b) Sexual competition among male blue crab, Callinectes sapidus. Biological Bulletin 13: Jivoff P, Hines AH (18a) Effect of female molt stage and sex ratio on courtship behavior of the blue crab Callinectes sapidus. Marine Biology 131: Jivoff P, Hines AH (18b) Female behaviour, sexual competition and mate guarding in the blue crab, Callinectes sapidus. Animal Behaviour 55: Jivoff PR, Able KW (23) Blue crab, Callinectes sapidus, response to the invasive common reed, Phragmites australis: Abundance, size, sex ratio, and molting frequency. Estuaries 26: Jordan SJ (18) The blue crab fisheries of North America: research, conservation, and management. Journal of Shellfish Research 17: Kennish MJ, Vouglitois JJ, Danila DJ, Lutz RA (184) Shellfish. In: Kennish MJ, Lutz RA (eds) Ecology of Barnegat Bay, New Jersey. Springer-Verlag, New York, pp Lipcius RN, Seitz RD, Seebo MS, Colon-Carrion D (25) Density, abundance and survival of the blue crab in seagrass and unstructured salt marsh nurseries of Chesapeake Bay. Journal of Experimental Marine Biology and Ecology 31: 6-8 Lipcius RN, Stockhausen WT (22) Concurrent decline of the spawning stock, recruitment, larval abundance, and size of the blue crab Callinectes sapidus in Chesapeake Bay. Marine Ecology- Progress Series 226: McConaugha JR, Johnson DF, Provenzano AJ, Maris RC (183) Seasonal distribution of larvae of Callinectes sapidus (Crustacea: Decapoda) in the waters adjacent to Chesapeake Bay. Journal of Crustacean Biology 3:

19 Mistiaen JA, Strand IE, Lipton D (23) Effects of environmental stress on blue crab (Callinectes sapidus) harvests in Chesapeake Bay tributaries. Estuaries 26: Stehlik LL, Scarlett PG, Dobarro J (18) Status of the blue crab fisheries of New Jersey. Journal of Shellfish Research 17: Tankersley RA, Wieber MG, Sigala MA, Kachurak KA (18) Migratory behavior of ovigerous blue crabs Callinectes sapidus - evidence for selective tidal-stream transport. Biological Bulletin 15: Uphoff JH (18) Stability of the blue crab stock in Maryland's portion of Chesapeake Bay. Journal of Shellfish Research 17: