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Leopard shark mating observed off La Jolla, California

  • Seiurus Biological Consulting
California Fish and Game 91(1):128-135 2005
Southwest Fisheries Science Center
8604 La Jolla Shores Drive
La Jolla, CA 92037
On 4 August 2003, mating behavior was observed in an aggregation of leopard
sharks, Triakis semifasciata, in shallow water near the surf zone along a sandy ocean
beach in La Jolla, California, approximately 21.6 km north of the entrance to San Diego
Bay. The following account provides the first documented observations of leopard
shark mating in the wild.
The leopard shark is an inshore coastal, largely benthic shark that is distributed from
southern Oregon south to Baja California, Mexico, including the upper Gulf of California
(Eschmeyer et al. 1983). Although it is reportedly common in enclosed muddy bays,
other habitats include flat sandy areas, mud flats, and bottoms strewn with rocks near
rocky reefs or kelp beds (Eschmeyer et al. 1983; Compagno 1984; Love 1991; PFMC
19981; Ebert 2003). It feeds mostly on small fishes and benthic invertebrates (Russo
1975; Smith 2001). The population is thought to be composed of various regional
subpopulations with limited exchange among them (Smith and Abramson 1990),
although no range-wide stock study has been undertaken to date. Because of their
restricted geographical range, shallow water distribution, and assumed limited exchange
among regional stocks, leopard sharks near large population centers may be vulnerable
to heavy localized fishing pressure and habitat disturbance. Stocks in California are
at least partially protected by commercial fishing area closures in inshore waters, a
recreational and commercial minimum size limit (91 cm total length (TL)) since 1992 and
1994, respectively, and a recreational bag limit of three fish since 1992.
Mating areas, behavior, and seasonality have not been documented for this
species, nor has critical habitat for reproduction been described. The occurrence of
large leopard shark aggregations, some of them numbering in the hundreds, is not
unusual for certain mud flat and sandy beach locations in California, including the La
Jolla study area (e.g., Eschmeyer et al. 1983; Ackerman et al. 2000, Anonymous 2000
a, b; Huard 2002; Ebert 2003). But little documentation exists concerning specific
behavior associated with these shoals. Some are presumed to be for the purposes of
foraging on organisms made accessible during periods of high tides (Ackerman et al.
1Pacific Fisheries Management Council (PFMC). 1998. Groundfish Essential Fish Habitat
Appendix. June 15, 1998. Prepared by Groundfish Core Team Casillas, E., L. Crockett, Y.
deReynier, J. Glock, M. Helvey, B. Meyer, C. Schmitt, and M. Yoklavich. NMFS
Northwest Region, Seattle, WA.
2000), others may represent females gathering in pupping areas. For example, there is
one documented report of dozens of pregnant females gathering in the shallow flats
in Catalina Harbor, giving birth to pups (Smith 2001). Neonate-sized pups are also
abundant seasonally along many protected southern California beaches and bays,
such as Santa Monica Bay, where they were once harvested for the aquarium trade
(Smith 2001).
Since 1991, the author has observed in the general study area numerous leopard
shark aggregations composed of large juveniles and adults numbering from 25 to 180
individuals, but with no obvious pupping, courting or mating behavior taking place2.
According to Kusher et al. (1992), females reach sexual maturity at approximately 105
cm TL; males at about 100 cm TL. The aggregations have been observed mainly during
midsummer through fall (July through November), with one observation of over a
hundred individuals in February 1996. Because viewing conditions must be optimum
(clear water, calm sea state, favorable light angle) to see the sharks from the cliff top,
and divers tend to disrupt the sharks’ normal activity and cause them to move away,
it has been difficult to observe detailed behavior to confirm whether mating, pupping
or feeding activity is taking place when the sharks form these aggregations. Also, it
is not known whether the peak in summer and early fall sightings is due to an actual
increase in this behavior or because viewing conditions are more favorable during this
period than during the stormy winter-spring period, when rain runoff reduces water
clarity and windier conditions disturb the sea surface. The probability of human
encounters with these groupings increases during the warmer months, when more
people frequent the beaches.
The purpose of this note is to document observed group mating activity and
associated habitat, as part of ongoing efforts to identify areas that may be important
for reproduction in this species.
Observations were made from a cliff-top vantage point overlooking the ocean
approximately 68 m above the southern end of Black’s Beach in La Jolla, California (Fig.
1). The leopard shark aggregation was viewed with the naked eye and with Leica 8X32
binoculars. All observations were made from the ocean-facing, 2nd floor walkway of the
National Marine Fisheries Service’s Southwest Fisheries Science Center at 8604 La Jolla
Shores Drive, La Jolla, CA. This area is located approximately 21.6 km north of the
entrance to San Diego Bay, and is adjacent to the head of Scripps Canyon, which comes
to within 305 m of shore at this location (Munk and Traylor 1947) (Fig. 1). The coastal
ocean off this beach is part of the Marine Life Refuge of the San Diego-La Jolla
Underwater Park system, the bottom consists of smooth sand, with a small reef of
sedimentary rock immediately adjacent to the south, which extends out from the beach.
The area is usually characterized by calmer sea conditions than beach areas 1 km to the
2S. E. Smith, unpublished data, NMFS, Southwest Fisheries Science Center, La Jolla, CA.
north (Black’s Beach surfing area) and immediately to the south (Scripps Institution
of Oceanography pier south to 32E51’48"N latitude) (Munk and Traylor 1947).
Figure 1. Map of the La Jolla, California area and location where leopard shark mating activity
was observed, showing proximity to Scripps Canyon.
The shark aggregation was observed at approximately 1400-1430 h (PDT) on 4
August 2003 off northern La Jolla Shores, San Diego, California (approx. 32E52'19.1"N,
117E15'14.8"W, Fig. 1). It was composed of a small group of nine leopard sharks located
approximately 20 m offshore, swimming in water 1-3 m deep. Judging from the size of
nearby Western Gulls (Larus occidentalis) resting on the surface nearby, individuals
in the aggregation appeared to be between 122-152 cm TL long. The sharks were milling
about in a relatively tightly spaced, almost circular-shaped group (Fig. 2). Most
members of the group were closer than a body length from each other, although once
a single individual strayed out of the circle a few meters, before immediately returning.
Physical measures taken at nearby Scripps Pier at 1416 h PDT were as follows: sea
bottom temperature, 17.4EC; sea level pressure, 1013.72 mb; wind speed, 11.4 km per
h; wind direction, WNW 285E; tide height, 1.60 m (high at 1504 h); sunlight intensity,
72%; moon phase, one-quarter.3 The data buoy at nearby Point La Jolla at 1400 hr PDST
recorded a sea surface temperature of 21.5EC, wave height of 0.85 m, peak and average
wave period of 14.29 and 6.87 seconds respectively, and mean wave direction from the
SSW (204E).4
For the first few minutes of observation, the sharks appeared to be milling randomly,
although intermittently an individual would tilt its body and briefly roll over, flashing
the white of its under belly before re-orienting itself in a normal swimming position.
Because of the distance and vantage point, it was not possible to distinguish sex
(presence or absence of claspers) of individuals in the group. The animals milled
smoothly, exhibiting mild agitation only when banking abruptly to maintain the group’s
cohesive, roughly circular shape. The frequent belly flashing appeared passive, and
not associated with avoidance of another aggressive individual in the group. Several
individuals, at least two simultaneously, were seen exhibiting this belly-flash behavior.
When the milling aggregation strayed laterally in any direction, it moved generally as
a unit, the individuals moving together but without parallel orientation. At one point,
in the center of the circular aggregation, a smaller-sized shark (presumably male, referred
to as shark No. 1), began to follow close behind another larger shark (presumably female,
shark No. 2). It then quickly moved forward and parallel to shark No. 2 and wrapped
its body around it (Fig.2). The two sharks then rolled together entwined, a slight forward
momentum still carrying them slowly in the direction they had originally been swimming,
then both appeared to rest on the bottom. They remained thus entwined for a period
estimated to be not more than 15 seconds, before separating. At the instant of
3Scripps Institution of Oceanography (SIO) Pier Weather. 2004. Data from 1916 to today. Pier
5-minute data archive. Scripps Institution of Oceanography, La Jolla, California. http:// (Accessed January 29, 2004).
4Scripps Institution of Oceanography (SIO) Coastal Data Information Program (CDIP). 2004.
Station Description for Point La Jolla, CA 095. Scripps Institution of Oceanography, La
Jolla, California. (Accessed January 29,
separation, just as the female broke away, a milky cloud (presumably seminal fluid),
billowed to the surface above their location. Others in the group did not appear to
interact with the pair during the brief copulation, but stayed in close proximity,
becoming less closely spaced after the pair had separated. The group remained
together for about 15 additional minutes, gradually spreading out over time, eventually
dispersing randomly and disappearing out of view. Total viewing time was approximately
30 minutes. No additional pairings or copulations were observed, although one animal
was seen to briefly roll and show the white of its belly before the group dispersed. No
obvious aggressive behavior or fin nipping was observed in any shark within the group.
However, when the two sharks were entwined, fin biting and holding may have
occurred. The head of shark No. 1 during coitus was positioned directly over shark No.
2’s right pectoral fin, and the entwining shark could have been holding the fin in its
mouth to gain purchase on shark No. 2.
Figure 2. Progression of courtship and copulation behaviors observed in a small group of leopard
sharks off La Jolla, CA, August 4, 2003, showing a) the milling group with pivot and belly flash
behavior; b) parallel swimming, and c) copulation at the center of the group.
Just as muddy bays, estuaries and sloughs serve as important habitat for this
species north of Point Conception, shallow, surf-protected areas along southern
California sandy beaches and coves may be similarly important to southern California
leopard sharks for feeding, pupping, and mating. Certainly the study area, and the La
Jolla Shores area to the south, are important leopard shark aggregating locations in San
Diego County, based on these and past observations and anecdotal accounts in this
same general area.
It has previously been assumed, but not confirmed, that mating takes place
sometime in summer after spring parturition (Smith and Abramson 1990). The mating
activity reported here, although brief in duration and viewed from a distance, provides
documentation that mating in the San Diego area occurs in summer, and can occur at
midday along sandy beaches in shallow water. In all elasmobranchs, copulation
requires the insertion of one or both claspers into the cloaca and oviduct or oviducts
of the female (Pratt and Carrier 2001). While it was impossible to observe this type of
detail from the distance observed, the presence of what appeared to be seminal fluid
in the water immediately after separation of the entwined pair, suggests that copulation,
however brief, took place.
Fin biting was not observed, but might have been obscured by the distance and
viewing angle (generally from above). Fin biting and holding have been reported for
courting leopard sharks in captivity (Manny Ezcurra and Kevin Lewand, Monterey Bay
Aquarium, pers. comm., 10/2003) and in other species of sharks in captivity and in the
wild (e.g., Klimley 1980; Castro et al. 1988; Pratt and Carrier 2001). In most elasmobranchs
in which mating behavior has been observed, the male bites and often holds the female,
apparently as a precopulatory releasing mechanism to invoke female acquiescence
during courtship, to facilitate insertion of the clasper, and to maintain proper position
and proximity until sperm transfer is complete (Pratt and Carrier 2001). Observations
of body wrapping are consistent with that reported for mating leopard sharks in
captivity (Ackerman citing Herald5; Manny Ezcurra and Kevin Lewand, pers. comm. 10/
2003) and mating in other slender, flexible sharks, in which there is a tendency for the
male to wrap its body around the female (Dempster and Herald 1961; Dral 1980). But
no group courtship or mating behavior has been reported for leopard sharks in
Unfortunately, the gender of individuals in the group observed in the wild at La Jolla
could not be determined directly, but based on the wrapping behavior and presence
of what appeared to be a sperm cloud, the central pair was likely male and female. It is
uncertain whether the group was polygynous (one male with several females),
polyandrous (one female with several males), or promiscuous.
5Ackerman, L. T. 1971. Contributions to the biology of the leopard shark, Triakis semifasciata
(Girard) in Elkhorn Slough, Monterey Bay, California. M.A. Thesis, Sacramento State
College, Sacramento, California, USA.
Pratt and Carrier (2001), in their review of elasmobranch reproductive behavior,
present a case study of mating behavior in the nurse shark Ginglymostoma cirratum,
a species that also mates in extremely shallow water. They suggest that females seek
out the shallows as a refuge from pursuing males from deeper water, but the males
nonetheless follow them there, where they encircle them in groups of 1 to 4 males per
female, often with much persistence. In the present case, members of the group milled
together smoothly, with no obvious indication of aggressiveness or male pursuit
behavior until the moment of abrupt parallel swimming and copulation exhibited by the
one pair. Also, the belly flashing observed here appeared to be more passive than the
tilt and roll behavior described by Pratt and Carrier (2001) as a female male-avoidance
This group of leopard sharks differed in size, cohesiveness, and behavior from other
daytime leopard shark aggregations the author has observed in the same area in the
past. Only nine individuals were observed, and these formed a tightly knit group, whose
members appeared to interact and display to each other with body tilts and belly flashes.
They remained together in a cohesive unit, before, during, and immediately after the
central pair copulated. Large aggregations previously seen by the author in the same
area (e.g., > 100 individuals) did not exhibit ‘close-following,’ ‘belly-flashing,’ or
copulatory behavior, and the only interaction occurred when a shark swam to one side
to avoid colliding with another. It is possible that these large, more diffuse daytime
aggregations are for the purposes of feeding (or preparing to feed later at night), while
mating aggregations tend to be smaller and more closely knit. Nonetheless, one cannot
entirely rule out that even these larger groupings, especially those seen during spring
and summer, may be gatherings preparatory to reproductive activity such as pupping
or mating. Additional and closer observation is needed by divers careful not to disturb
the sharks, or with unobtrusive, remotely operated vehicles or cameras.
G. Cailliet, C. Dawson, M. Ezcurra, D. Holts, K. Lewand, W. Pratt, and D. Ramon,
made comments or provided information that led to improvements and clarifications in
early drafts of this work. I also thank C. Lane, D. Parker, and an anonymous reviewer
for helpful comments on the final draft. Roy Allen prepared the figures from my rough
sketches during a time that was especially busy for him. Special thanks to Manny
Ezcurra and Kevin Lewand (Monterey Bay Aquarium) for providing information on
leopard shark mating behavior in captivity.
Ackerman, J.T., M.C. Kondratieff, S.A. Matern, and J.J. Cech, Jr. 2000. Tidal influence on
spacial dynamics of leopard sharks, Triakis semifasciata, in Tomales Bay, California.
Environmental Biology of Fishes 58: 33-43.
Anonymous. 2000a. Leopard sharks, by the hundreds, are back. San Diego Union Tribune Jul
29 2000, p. B.5.
Anonymous. 2000b. Sharks by the shore. San Diego Union Tribune Sep 13, 2000, p. A1.
Castro, J.I., P.M. Bubucis, and N.A. Overstrong. 1988. The reproductive biology of the chain
dogfish, Scyliorhinus retifer. Copeia 1988 (3), pp. 740-746.
Compagno, L.J.V. 1984. FAO Species Catalogue Volume 4, Sharks of the World, Part 2.
Carcharhiniformes. FAO Fish Synopsis 125: 251-655.
Dempster, R.P. and E.S. Herald. 1961. Notes on the horn shark, Heterodontis francisci, with
observations on mating activities. Occasional Papers California Academy of Sciences 33: 1-
Dral, A.J. 1980. Reproduction en aquarium du requin de fond tropical, Chiloscyllium griseum
Müll. et Henle (Oretolobidés). Revue francais Aquariologie 7: 99-104.
Ebert, D. A. 2003. Sharks, rays and chimeras of California. California Natural History Guides
No. 71, University of California Press, Berkeley and Los Angeles, California, U.S.A.
Eschmeyer, W.N., E.S. Herald, and H. Hammann. 1983. A field guide to Pacific Coast fishes
of North America from the Gulf of Alaska to Baja California. Houghton Mifflin Company,
Boston, Massachusetts, U.S.A.
Huard, R. 2002. Swim with the sharks. San Diego Union Tribune. Aug 12 2002, p. B1.
Klimley, A. P. 1980. Observations of courtship and copulation in the nurse shark Ginglymostoma
cirratum. Copeia 1980 (4), pp. 878-882.
Love, M.S. 1991. Probably more than you want to know about the fishes of the Pacific Coast.
Really Big Press, Santa Barbara, California, U.S.A.
Munk, W.H. and M. A. Traylor. 1947. Refraction of ocean waves: a process linking underwater
topography to beach erosion. Journal of Geology 55(1):1-26.
Pratt, H. L. Jr., and J. C. Carrier. 2001. A review of elasmobranch reproductive behavior with
a case study of the nurse shark, Ginglymostoma cirratum. Environmental Biology of Fishes
60, 157-188.
Russo, R.A. 1975. Observations on the food habits of leopard sharks (Triakis semifasciata)
and brown smoothhounds (Muselus henlei). California Fish and Game 61:95-103.
Smith, S.E. 2001. Leopard shark, p. 252-254. In (W.S. Leet, C.M. Dewees, R. Klingbiel, and
E. J. Larson, eds), California’s Living Marine Resources: A Status Report. California
Department of Fish and Game. University of California Agriculture and Natural Resources.
Sea Grant Publication SG01-11.
Smith, S.E. and N. Abramson. 1990. Leopard shark Triakis semifasciata distribution, mortality
rate, yield, and stock replenishment estimates based on a tagging study in San Francisco Bay.
Fishery Bulletin, U.S. 88(2):371-381.
Received: 18 April 2004
Accepted: 9 August 2004
... one of the most researched elasmobranchs along the Pacific Coast of North America with several aspects of its biology well defined (Ackerman 1971;Russo 1975Russo , 2013Russo , 2015Russo , 2018Russo , 2019Talent 1976Talent , 1985Smith 1984Smith , 2001Smith , 2005Smith and Abramson 1990;Cailliet 1992;Kusher et al. 1992;Au and Smith 1997;Smith et al. 2003;Hight and Lowe 2007;Lewallen et al. 2007;Starr 2009, 2010;Nosal et al. 2013aNosal et al. ,b, 2014Launer 2014;Barker et al. 2015). Various reproductive studies have occurred for leopard sharks (Ackerman 1971;Talent 1985;Ebert and Ebert 2005;Smith 2005;Nosal et al. 2013aNosal et al. , b, 2014Launer 2014;Russo 2015Russo , 2018Russo , 2019. ...
... one of the most researched elasmobranchs along the Pacific Coast of North America with several aspects of its biology well defined (Ackerman 1971;Russo 1975Russo , 2013Russo , 2015Russo , 2018Russo , 2019Talent 1976Talent , 1985Smith 1984Smith , 2001Smith , 2005Smith and Abramson 1990;Cailliet 1992;Kusher et al. 1992;Au and Smith 1997;Smith et al. 2003;Hight and Lowe 2007;Lewallen et al. 2007;Starr 2009, 2010;Nosal et al. 2013aNosal et al. ,b, 2014Launer 2014;Barker et al. 2015). Various reproductive studies have occurred for leopard sharks (Ackerman 1971;Talent 1985;Ebert and Ebert 2005;Smith 2005;Nosal et al. 2013aNosal et al. , b, 2014Launer 2014;Russo 2015Russo , 2018Russo , 2019. Although these studies have found sexual segregation the specifics of male sexual maturity remain unknown. ...
Full-text available
Determining sexual maturity in male leopard sharks, Triakis semifasciata, requires calcified claspers, a body length exceeding 92.7 cm TL and the presence of spermatozoa in the seminal and sperm sacs along with coiled vas deferens. . A delay occurs between the onset of calcification and the commencement of sperm production. Alll three criteria must be met before one can predict sexual maturity. The length and calcification alone are insufficient factors in determining sexual maturity.
... In central and northern California, parturition appears to occur from March through September, with a peak in April and May (Ackerman 1971, Talent 1985, Smith and Abramson 1990, Ebert and Ebert 2005. In southern California pupping is believed to occur around May and June, although it has been reported to occur as late as September in San Diego Bay (Eigenmann 1891, Smith 2005. Mating is believed to occur shortly after pupping (Ackerman 1971, Talent 1985, Ebert 2003 and has only been observed once in the wild, in the shallow surf zone in La Jolla (Smith 2005). ...
... In southern California pupping is believed to occur around May and June, although it has been reported to occur as late as September in San Diego Bay (Eigenmann 1891, Smith 2005. Mating is believed to occur shortly after pupping (Ackerman 1971, Talent 1985, Ebert 2003 and has only been observed once in the wild, in the shallow surf zone in La Jolla (Smith 2005). Females may mate with multiple males with as many as 36% of litters having multiple paternity (Nosal et al. 2013b). ...
Full-text available
Leopard Shark (Triakis semifasciata) is one of the most common nearshore sharks along the Pacific coast of North America, ranging from Washington to Mazatlan, Mexico, including the Gulf of California. They appear to exhibit limited long distance movement, and as a result it is thought that the population consists of three regional population clusters in northern California, southern California and Mexico with limited genetic exchange. In California, where nearly all of the U.S. harvest occurs, the Leopard Shark is taken primarily by recreational anglers, although it is also caught incidentally in commercial fisheries. The species has also been harvested for the cold-water aquarium trade and has been highly prized for its distinctive markings and hardiness. Due to its rather limited geographical range and limited exchange among regional stocks, resident stocks near large population centres may be particularly vulnerable to heavy localized fishing pressure. However, this species does not appear to be at risk judging by the combined landings in relation to previously calculated estimates of fishing mortality and exploitation rates. Additionally, current conservation and regulatory actions enacted by the California Department of Fish and Wildlife appear to have reduced these rates and have contributed significantly toward protecting this species from excessive harvesting in recent years and there is evidence that the leopard shark population has been increasing as a result of these management actions. Little is known of the biology, historical population abundance and full extent of harvest of this species in Mexican waters, but it is estimated to be less than one percent of the Pacific Ocean catch off Baja California and rarely caught in the Gulf of California. As a result of the success of the conservation measures taken in the U.S. and the lack of a significant fishery in Mexican waters, this species is assessed as Least Concern. However, due to the fact that this species is endemic to this region, is subjected to recreational fishing and bycatch pressures (albeit regulated in the U.S.), is susceptible to overfishing due to its life history characteristics (slow growing, long lived, late maturing, low productivity), and is impacted by habitat loss and degradation, it is important to continue managing and monitoring the species to ensure the health of the species.
... Habitat alteration and loss as a result of erosion could alter the abundance of resident fauna (Lindquist 1998;Carlisle et al. 2007), distribution of higher trophic levels (Lindquist 1998), and disrupt the function of nursery habitat (Yoklavich et al. 1991;Lindquist 1998 (Nosal et al. 2013). A large aggregation in La Jolla was the first documented mating of Leopard Sharks the wild (Smith 2005). Hight and Lowe (2007) documented female Leopard Sharks aggregating in warmer areas near the Catalina Islands. ...
... One potential cause of sexual segregation could be female avoidance of mating attempts from aggressive males. This does not seem likely, however, as observations of mating between wild Leopard Sharks indicate that mating attempts are not aggressive, though pectoral biting during copulation has been observed (Smith 2005). Smith (2005) described an aggregation of Leopard Sharks circling and potentially exhibiting mating displays though sex identification was not possible from her vantage point. ...
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Estuaries are used seasonally by many elasmobranchs for reproduction and as nurseries. The character, location, and availability of elasmobranch habitats in estuaries are often altered by anthropogenic activities and environmental changes. These habitat changes may have different effects on groups within a shark population because sexspecific segregations are common for many elasmobranchs. Leopard Sharks (Triakis semifasciata) are important estuarine predators in California and exhibit sexual segregations. Movements of 13 Leopard Sharks (male n=6, female n=7) tagged with coded acoustic transmitters were monitored from March 14, 2013 to March 9, 2014 using moored receivers in Elkhorn Slough, CA. Movement patterns were compared by region within Elkhorn Slough and related to environmental variables. Tagged individuals of both sexes spent the majority of time in the middle section of Elkhorn Slough, though females were more frequently present early in the day and uncommonly recorded after noon; males consistently used the middle section of Elkhorn Slough throughout the day. The monthly number of hours male Leopard Sharks were detected in the study site was positively correlated with water temperature and female Leopard Shark detected hours were negatively correlated with dissolved oxygen concentration. Differences in frequency of detection at temperatures ranging from 13°-16° C were dependent on sex and region of Elkhorn Slough.
... Although mating has been observed in only a few species, the pectoral grasp, rolling into head-down or ventral-side-up postures, and erratic tailbeating exhibited by nurse sharks have been observed in a number of other species. These include Triaenodon obesus (Tricas & LeFeuvre 1985, Whitney et al. 2004, Hemiscyllium freycineti (Cornish 2005), Triakis semifasciata (Smith 2005), Heterodontus portusjacksoni (Powter & Gladstone 2008), Carcharhinus amblyrhynchos (Y. Hubert pers. ...
... Although mating has been observed in only a few species, the pectoral grasp, rolling into head-down or ventral-side-up postures, and erratic tailbeating exhibited by nurse sharks have been observed in a number of other species. These include Triaenodon obesus (Tricas & LeFeuvre 1985, Whitney et al. 2004, Hemiscyllium freycineti (Cornish 2005), Triakis semifasciata (Smith 2005), Heterodontus portusjacksoni (Powter & Gladstone 2008), Carcharhinus amblyrhynchos (Y. Hubert pers. ...
... The largest shark count in any single photograph was 125, however, additional sharks were likely outside the field of view. Sharks were in constant motion and exhibited very few conspicuous formations or behaviors except for brief bouts (a few seconds, visible in no more than 5-10 sequential photographs) of circling, following, and occasionally turning over to expose their white ventral surfaces (see Klimley 2003, Smith 2005; Fig. 2c). The sharks' movements are best described as milling, lacking any obvious unimodal polarization (i.e., sharks were not oriented in the same direction). ...
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The demography, spatial distribution, and movement patterns of leopard sharks (Triakis semifasciata) aggregating near the head of a submarine canyon in La Jolla, California, USA, were investigated to resolve the causal explanations for this and similar shark aggregations. All sharks sampled from the aggregation site (n = 140) were sexually mature and 97.1 % were female. Aerial photographs taken during tethered balloon surveys revealed high densities of milling sharks of up to 5470 sharks ha−1. Eight sharks were each tagged with a continuous acoustic transmitter and manually tracked without interruption for up to 48 h. Sharks exhibited strong site-fidelity and were generally confined to a divergence (shadow) zone of low wave energy, which results from wave refraction over the steep bathymetric contours of the submarine canyon. Within this divergence zone, the movements of sharks were strongly localized over the seismically active Rose Canyon Fault. Tracked sharks spent most of their time in shallow water (≤2 m for 71.0 % and ≤10 m for 95.9 % of time), with some dispersing to deeper (max: 53.9 m) and cooler (min: 12.7 °C) water after sunset, subsequently returning by sunrise. These findings suggest multiple functions of this aggregation and that the mechanism controlling its formation, maintenance, and dissolution is complex and rooted in the sharks’ variable response to numerous confounding environmental factors.
... Although mating has been observed in only a few species, the pectoral grasp, rolling into head-down or ventral-side-up postures, and erratic tailbeating exhibited by nurse sharks have been observed in a number of other species. These include Triaenodon obesus (Tricas & LeFeuvre 1985, Whitney et al. 2004, Hemiscyllium freycineti (Cornish 2005), Triakis semifasciata (Smith 2005), Heterodontus portusjacksoni (Powter & Gladstone 2008), Carcharhinus amblyrhynchos (Y. Hubert pers. ...
Full-text available
Little is known about the reproductive strategies and mating behaviour of most sharks. Understanding mating behaviour is important as it can determine reproductive success and possibly rates of multiple paternity and fecundity. Additionally, some sharks appear to have specific habitat requirements for mating activities. We tested the utility of a 3-dimensional acceleration logger to identify mating events in free-living nurse sharks Ginglymostoma cirratum in an area where behaviours can be observed directly, thus allowing corroboration of acceleration data. Loggers were attached to 4 adult females and were recovered after recording periods of 23.2 to 99.8 h (mean ± SD = 50.0 ± 35.1 h). We used acceleration data to classify several behaviours, including swimming, resting, resting in a surge zone, and mating, with examples of each behaviour confirmed via direct observation. Twenty-six mating events were inferred from acceleration data, ranging from 21 s to 20.1 min in duration (median = 2.22 min), with no events taking place during the nighttime hours between 23:00 and 07:00 h. Four events lasted longer than 9 min and took place during periods when loggerequipped sharks were not acoustically detected within the shallow study site. The similarity in mating behaviours between this and some other species raises the possibility that accelerometry could be used to quantify mating in a variety of shark species. This is the first study to classify mating and other behaviours in free-living sharks from acceleration data.
... It may be that these sharks mate at a different time of year and store sperm in the shell gland, as has been reported for the blue shark, Prionace glauca (Pratt 1979). Smith (2005) observed mating in T. semifasciata in La Jolla Cove, San Diego, California, in August 2001. If the timing of Smith's observation, late summer, is indicative of the time of year mating takes place in T. semifasciata this would be 2-3 months after parturition. ...
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A total of 312 female leopard sharks (Triakis semifasciata) was sampled in Humboldt Bay, California, USA, an important nursery ground for this species, during the spring month of May from 1983 to 1984 and 1985. Sexual segregation is strong as only three males were observed in the study area. Females ranged in size from 120 to 154 cm total length, and all examined were determined to be mature. Overall, 130 out of 153 females examined in early May contained term embryos. The number of embryos per female ranged from 1 to 37 with larger females tending to possess more embryos. Of the 159 individuals examined in late May, no females were found carrying embryos and most were ovulating. Diet analyses revealed that, overall, fish eggs (Atherinopsis californiensis) at 48.0%, had the highest percentage Index of Relative Importance (%IRI), followed by the cancrid crabs, Cancer antennarius (29.8%) and C. magister (11.6%). All other prey were of relatively minor importance, cumulatively representing 10.6% of the overall diet. Adults shift their diet after parturition: early May sharks fed almost exclusively on fish eggs, while crabs were more important in those examined in late May.
... Females of these species often remain closer to their home territories, while males roam farther away. In California, nine locations are suspected breeding sites for leopard sharks: Humboldt Bay, Tomales Bay, Bodega Bay, San Francisco Bay, Elkhorn Slough, Morro Bay, Santa Monica Bay (Los Angeles), Catalina Harbor (Santa Catalina Island), and San Diego Bay (Talent 1985;Monaco et al. 1990;Smith and Abramson 1990;Ebert and Ebert 2005;Fowler et al. 2005;Smith 2005; G. Cailliet, personal communication; D. Ebert, personal communication; S. Smith, personal communication). Six of these breeding locations were sampled during this study and this information was later used to partition data for tests of philopatry. ...
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The leopard shark (Triakis semifasciata) is an important predator in coastal marine ecosystems of California, targeted by recreational and commercial fishermen and of specific interest in fisheries management. From October 2003 to August 2006, 169 leopard sharks were collected from the coast of California (between 40.750°N and 32.678°N) and analyzed for mitochondrial and nuclear genetic structure. Analyses of mtDNA control region sequences revealed relatively low levels of genetic variation (five haplotypes, average pairwise divergence π=0.0067). In contrast, leopard sharks were highly polymorphic for inter simple sequence repeats (ISSRs), which characterize a broad range of the nuclear genome. The null hypothesis of panmixia in California waters was rejected for both genetic markers, and ISSRs displayed a statistically significant pattern of isolation by distance (IBD) across the species range (P=0.002). A variety of analyses showed that divergence is most pronounced in the northernmost population of Humboldt Bay. Natal philopatry in T. semifasciata was tested using Siegel-Tukey tests on data partitioned by breeding site status, and sex-specific philopatry was tested by comparing IBD plots between sexes. Although there was some evidence for natal philopatry in leopard sharks (P=0.038), and population divergence may be related to the proximity of breeding sites (P=0.064), we found no support for sex-specific philopatry. In addition to identifying a novel set of highly variable genetic markers for use in shark population studies, these results may be used to better inform management decisions for leopard sharks in California.
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Leopard shark tag covery data, obtained from a 1979-88 study in San Francis00 Bay, were analyzed to determine temporal and geographic distribution of the tagged population. V i population analysis of the tag recovery data was used to derive fishing mortality rates, which in turn were used to obtain yield-per-recruit and stock replacement values, and to estimate the effect of management by size limit on stock replenishment and yield per recruit. Of the tagged population, 11% was recovered by sport anglers and commercial fishermen, and the distribution of recoveries indicates that leopard sharks are mostly resident in San Francisco Bay, although a portion of the population moves out of the Bay during fall and winter. An unusually high number of recaptures was made in 1983, a year of El Nifio conditions and high river runoff. After obtaining mortality, yield, and stock replacement values, it was proposed that a viable management strategy for the San Francisco Bay leopard shark would be a size limit of 100 cm or 40 inches to ensure maintenance of the stock and provide a yield per recruit not too far below a maximum.
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Reproduction, embryonic development, and general biology are described from more than 100 chain dogfish, Scyliorhinus retifer, a common catshark found on the continental slopes of the western North Atlantic. Females and males reached sexual maturity at about 520 mm TL and 500 mm TL, respectively. Follicles are ovulated in pairs when they reach 18 mm diameter. In the laboratory, females lay one egg pair at approx. 15.3 d intervals, attaching the eggs to bottom structures. Development at 11.7-12.8 C in artificial seawater averaged 256 d (±SD 8 d, n = 62) to hatching. Embryos averaged 106 mm (±SD 5 mm, n = 63) at hatching. In the wild, juveniles are often found in large numbers over smooth bottoms. Adults congregate in areas with upright structures which females use for egg attachment. Chain dogfish feed on squid, small bony fishes, polychaete worms, and crustaceans.
Elasmobranch reproductive behavior has been inferred from freshly caught specimens, laboratory examinations of reproductive structures and function, or determined from direct observations of captive or free swimming wild animals. Several general behaviors have been described including seasonal sexual segregation, courtship and copulation. Courtship behavior was inferred for many species from the presence of scars and tooth cuts on the female's body, and noted in more detail from underwater observations. Copulation has been directly observed in captive settings for several species of elasmobranchs in large aquaria, and in the wild for three species of urolophids and for Triaenodon obesus and Ginglymostoma cirratum. A detailed ‘case history’ of nurse shark reproductive behavior is presented that may be used as a template for future work on shark reproductive behavior of other species. Our studies, using diver identifiable tags and in situ behavioral observations, provide unprecedented information on social structure and mating behavior in this species. Since 1993, 115 G. cirratum, 45 adults and 70 juveniles have been tagged in the Dry Tortugas, Florida. Observations show that adult males visit the study site every year with three males dominant. Individual adult females visit the study area to mate in alternate years. Polygyny and polyandry are common. Future research on reproductive behavior of elasmobranchs should address questions on male access to females, sexual selection and dominance hierarchies.
We used ultrasonic telemetry to determine the movement directions and movement rates of leopard sharks, Triakis semifasciata, in Tomales Bay, California. To analyze tide and time of day effects, we surgically implanted transmitters in the peritoneal cavities of one male and five female leopard sharks, which we located during summer for three to five sampling sessions lasting 12 to 24h each. All leopard sharks showed strong movement direction patterns with tide. During incoming tides, sharks moved significantly (p