Harold Pratt

Anderson Cabot Center for Ocean Life, New England Aquarium · Fisheries Science and Emerging Technologies Program

Basking sharks (Cetorhinus maximus) seasonally aggregate in coastal surface waters of the North Atlantic, providing opportunities for visual observation. While putative courtship displays have been observed, actual copulation has not been documented. Here we examine video collected by an unmanned aerial vehicle (“drone”) of novel behavioral interac...

In this review of the behavioural patterns of chondrichthyan fishes, we have strived to produce a comprehensive catalogue of events and states and develop standardized terminology. Hence, actions that are slightly different, will be pooled under inclusive titles. Those used by different investigators are included in quotations within the textual de...

Elasmobranchs have elaborate organ systems for reproduction and many have complex reproductive life histories, but we are just beginning to understand that elasmobranchs may also exhibit involved pre-copulatory and copulatory and group behaviors. Shark, skate and ray behavior has been generally dismissed as unsophisticated by both biologists and no...

Elasmobranchs have elaborate organ systems for reproduction and many have complex reproductive life histories, but we are just beginning to understand that elasmobranchs may also exhibit involved pre-copulatory group courtship, mating and copulatory behaviors . Shark, skate and ray behavior has been generally dismissed as unsophisticated by both bi...

Animals sometimes forage in mixed species groups, where an individual of a “follower” species actively trails a foraging individual of another “nuclear” species to benefit from the latter’s foraging strategy. Here, we report on a serendipitous observation of a large, benthic, reef-associated predator, the nurse shark ( G. cirratum ) following a pod...

Understanding shark mating dynamics and mating site use may be vital to species management. The Dry Tortugas courtship and mating ground (DTCMG) has been known as a mating site for nurse sharks, Ginglymostoma cirratum, since 1895. In a 30-yr (1992–2021) study we have documented long-term site fidelity to this area with data from 137 adult sharks (8...

Nurse sharks have not previously been known to migrate. Nurse sharks of the Dry Tortugas (DRTO) mating population have a highly predictable periodic residency cycle, returning to the Dry Tortugas Courtship and Mating Ground (DTCMG) annually (males) or bi- to triennially (females) during the June/July mating season. For 23 years we have followed the...

We determined the complete mitochondrial genome sequence of nurse shark Ginglymostoma cirratum. The circular DNA of 16692 bp comprises 13 protein-coding genes, 22 transfer RNAs, 2 ribosomal RNAs, a non-coding control region and a non-coding origin of light strand replication with typical gene order of vertebrates. The nurse shark formed a well-supp...

Despite recent advances in field research on white sharks (Carcharodon carcharias) in several regions around the world, opportunistic capture and sighting records remain the primary source of information on this species in the northwest Atlantic Ocean (NWA). Previous studies using limited datasets have suggested a precipitous decline in the abundan...

To determine habitat-use patterns of sub-adult hawksbills Eretmochelys imbricata, we conducted satellite-and acoustic-tracking of 3 turtles captured in August 2008 within Dry Tortugas National Park (DRTO), south Florida, USA, in the Gulf of Mexico; turtles ranged in size from 51.9 to 69.8 cm straight carapace length. After 263, 699, and 655 d of re...

Polyandry has been demonstrated in a number of shark species. Studies based on a small number of loci typically estimate the minimum number of sires, which may be much lower than the actual number of sires due to the sharing of alleles by parents. We genotyped three litters of Nurse Shark (Ginglymostoma cirratum) ranging in size from 29 to 39 pups...

Age and growth rate of shortfin mako, Isurus oxyrinchus, captured by hook and line between 1961 and 1981 were determined using four methods: (1) temporal analysis of length–month information, (2) results of tagging data, (3) length–frequency analysis, and (4) ring counts on vertebrae. A temporal analysis of length–month information relating size to...

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...

A comprehensive population dynamics analysis of porbeagle shark (Lamna nasus) in the Northwest Atlantic indicates that the population has collapsed for the second time in its 43-year fishing history. The virgin population in the early 1960s supported annual catches of over 9,000 metric tons (t) before the fishery collapsed in 1967. After a partial...

Sharks are top predators in many marine ecosystems. Despite recent concerns over declines in shark populations, studies of shark communities in coastal habitats are limited. We used drumlines and longlines to determine shark community composition and habitat affinities in the Florida Keys, USA. Community composition varied among habitats. Catch rat...

Whirl-pak [R] and similar "fold-and-twist" blended polyethylene bags (FATs) are excellent containers for many types of biological samples because they are shatter-proof, lightweight, flat and thin when empty, less expensive than glass containers, nearly transparent, and available in a variety of sizes. Nevertheless, experience suggests that few kno...

A 12-year study of nurse shark Ginglymostoma cirratum reproduction in the islands of the Dry Tortugas, Florida has shown continued use of a 0.8-square-hectare shallow lagoon by sharks in all life stages from neonate through adult. Adults breed here every year during the June and July mating season. Juveniles use the same lagoon until they are about...

We analysed video records of three mating events involving nine free-living whitetip reef sharks in Cocos Islands, Costa Rica to examine reproductive behaviour in this species. We describe several behaviours never before documented in this species, and four behaviours never before documented in any elasmobranch. Here, we also present the first hypo...

The elasmobranchs have had an incredibly long evolutionary history: more than 400 million years. During this extensive period elasmobranchs separately evolved many adaptations such as exquisite senses and complex reproductive modes that rival those of the most advanced tetrapods. In this chapter we review the reproductive adaptations of the elasmob...

Over a period of 3 years, five reproductively active female nurse sharks (Ginglymostoma cirratum) from a wild, actively mating population of nurse sharks were captured, confined, and periodically examined through the course of gestation to determine the gestation period and characterize paternity. In the final year of the study, candidate animals w...

2002. Analysis of stomach contents of the porbeagle shark (Lamna nasus Bonnaterre) in the northwest Atlantic. – ICES Journal of Marine Science, 59: 1263–1269. Stomachs of 1022 porbeagle sharks (Lamna nasus) ranging in size from 85–264 cm were examined from the Canadian porbeagle shark fishery and a scientific cruise in the northwest Atlantic betwee...

Reproductive organs from 393 male and 382 female porbeagles (Lamna nasus), caught in the western North Atlantic Ocean, were examined to determine size at maturity and reproductive cycle. Males ranged in size from 86 to 246 cm fork length (FL) and females ranged from 94 to 288 cm FL. Maturity in males was best described by an inflection in the relat...

For over a decade, we have been studying the reproductive behavior of the nurse shark, Ginglymostoma cirratum, in the Dry Torugas off the Florida Keys, an important mating and nursery ground for this species. In the course of these studies, we have used a variety of tags and tagging protocols to monitor individual animals. Here we report the use of...

A virgin population of porbeagles Lamna nasus in the northwest Atlantic Ocean supported annual catches of up to 9,000 metric tons (mt) in the early 1960s before the fishery collapsed in 1967. Low and apparently sustainable catches of about 350 mt in the 1970s and 1980s allowed the stock to partially rebuild before a new fishery arose in the early 1...

During the spring and summer months of 1995, 1996 and 1997, gillnet and longline surveys were conducted in conjunction with tag and recapture experiments to outline spatial and seasonal distribution of young sandbar sharks, Carcharhinus plumbeus, in Delaware Bay for essential fish habitat mapping, to assess abundance of young sandbar sharks, and to...

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...

Sandbar shark (Carcharhinus plumbeus) populations on the US east coast have undergone several decades of decline due to fishing pressure. One strategy for rebuilding stocks is improved survival of young sharks through enhancement of nursery areas. A key element for understanding the dynamics of shark nursery areas is increased knowledge about essen...

Fifty mating events in free-living nurse sharks (Ginglymostoma cirratum) were observed over a nine-day period in the Dry Tortugas island cluster in the Florida Keys. Four stages of mating were identified: precoupling, coupling, positioning and alignment, and insertion and copulation. Copulation was observed and filmed in four of the mating events....

Two basic types of spermatozoan aggregates, spermatophores and spermatozeugmata, found in 14 different species of sharks, one species of skate, and one species of chimaera (holocephalan), were investigated using light and scanning electron microscopy. Spermatophores, aggregates (usually 1,000-6,000 microns in diameter and larger) of randomly clumpe...

Spermatozoa stored in oviducal glands of sharks sampled off the North American east coast were revealed by viewing stained tissue sections using light microscopy. Of eleven species surveyed, sperm were found in nine:Alopias vulpinus, Lamna nasus, Carcharhinus obscurus, Carcharhinus plumbeus, Galeocerdo cuvieri, Prionace glauca, Rhizoprionodon terra...

A large (4.6 m) white shark was followed for 3.5 days while its depth, water temperature and muscle temperature were recorded by acoustic telemetry. During this time the shark moved 190 km from an area south of Montauk Point, New York to Hudson Canyon. It made a number of brief excursions to the surface and to the bottom, but usually swam in the th...