Spatio-Temporal Variability in White Shark (Carcharodon carcharias) Movement Ecology During Residency and Migration Phases in the Western North Atlantic

Understanding how mobile, marine predators use three-dimensional space over time is central to inform management and conservation actions. Combining tracking technologies can yield powerful datasets over multiple spatio-temporal scales to provide critical information for these purposes. For the white shark (Carcharodon carcharias), detailed movement and migration information over ontogeny, including inter- and intra-annual variation in timing of movement phases, is largely unknown in the western North Atlantic (WNA), a relatively understudied area for this species. To address this need, we tracked 48 large juvenile to adult white sharks between 2012 and 2020, using a combination of satellite-linked and acoustic telemetry. Overall, WNA white sharks showed repeatable and predictable patterns in horizontal movements, although there was variation in these movements related to sex and size. While most sharks undertook an annual migratory cycle with the majority of time spent over the continental shelf, some individuals, particularly adult females, made extensive forays into the open ocean as far east as beyond the Mid-Atlantic Ridge. Moreover, increased off-shelf use occurred with body size even though migration and residency phases were conserved. Summer residency areas included coastal Massachusetts and portions of Atlantic Canada, with individuals showing fidelity to specific regions over multiple years. An autumn/winter migration occurred with sharks moving rapidly south to overwintering residency areas in the southeastern United States Atlantic and Gulf of Mexico, where they remained until the following spring/summer. While broad residency and migration periods were consistent, migratory timing varied among years and among individuals within years. White sharks monitored with pop-up satellite-linked archival tags made extensive use of the water column (0–872 m) and experienced a broad range of temperatures (−0.9 – 30.5°C), with evidence for differential vertical use based on migration and residency phases. Overall, results show dynamic inter- and intra-annual three-dimensional patterns of movements conserved within discrete phases. These results demonstrate the value of using multiple tag types to track long-term movements of large mobile species. Our findings expand knowledge of the movements and migration of the WNA white shark population and comprise critically important information to inform sound management strategies for the species.

Some Copepoda Parasitic on Fishes of the New Zealand Region

<p>Material representing 38 species of parasitic Copepoda, Order Caligoida, from New Zealand marine fishes, belonging to 20 genera and six families is discussed. Except for Lepeophtheirus erecsoni Thomson, of which only damaged material was available, the species are described and figured in detail. Previous records from New Zealand waters are discussed. The name Caligus vicarius is proposed for C. longicaudatus Brady which is preoccupied. Species examined and their hosts are as follows (new hosts for previously known species, and previously known species newly recorded from New Zealand are marked with asterisks) - Caligidae: Caligus brevis Shiinox on Pseudolabrus pittensisx, P. milesx and P. celidotusx; C. aesopus Wilsonx on Seriola grandisx; C. pelamydis Kroyerx on Thyrsites atunx; C. buechlerae Hewitt on Tripterygion sp.; Lepeophtheirus erecsoni Thomson on Latridopsis ciliaris; L. scutiger Shiinox on Pseudolabrus pittensisx, P. milesx and P. celidotusx; L. insignis Wilsonx on Mola mola; L. polyprioni Hewitt on Polyprion oxygenios and P. moeone; L. argentus Hewitt on Hyperoglyphe porosa; L. heegaardi Hewitt on Lepidopus caudatus; L. distinctus Hewitt on Genypterus blacodes; Euyphoridae: Gloiopotes huttoni (Thomson) on Makaira mitsukurii and M. marlina; Elytrophora brachyptera Gerstaekerx on Thunnus alalunga and. T. maccoyix; Pandaridae: Nesippus orientalis Hellerx on Mustelus antarcticus and Notorhynchus pectorosusx; N. borealis (Steenstrup and Lutken)x on Isurus oxyrinchusx; Dinemoura latifolia Steenstrup and Lutken on Carcharodon carcharias, Isurus oxyrinchus and Galeorhinus australis; D. producta (Muller) on Cetorhinus maximus and Carcharodon carcharias; Demoleus latus Shiinox on Squalus acanthiasx; Echthrogaleus braccatus (Dana) on an unrecorded host; E. coleoptratus (Guerin)x on Prionace glauca and Lamna nasus; E. denticulatus Smith on an unrecorded host; Phyllothyreus cornutus (Milne-Edwards)x on Isurus oxyrinchus; Pandarus bicolor Leachx on Squalus acanthias, Galeorhinus australisx, Notorhynchus pectorosusx and Cyprimulus sp.x; P. cranchii Leach on Galeorhinus australisx and Isurus oxyrinchus; Perissopus dentatus Steenstrup and Lutkenx on a hammerhead shark; Cecropidae: Cecrops latreillii Leach on Mola mola; Eudactylinidae: Nemesis lamna Rissox on Carcharodon carcharias, Cetorhinus maximus and Isurus oxyrinchus; N. robusta (van Beneden)x on Alopias vulpinus; Congericola pallidus van Benedenx on Conger vereauxix Dichelesthiidae; Pseudocycnus appendiculatus Hellerx on Thunnus alalunga; a new species of Hatschekia on Allomycterus jaculiferus; a further new species of Hatschekia on Lepidopus caudatus; Anthosomidae: a new species of Pseudolernanthropus on Thyrsites atun and Jordanidia solandri; a new species of Lernanthropus on Seriolella brama; Aethon percis (Thomson) on Parapercis coelias; two new species of Aethon on Cheilodactylus macropterus and Latridopus caudatues; Anthosoma crassum (Abildgaard) on Carcharodon carcharias, Isurus oxyrinchus, Lamna nasus and Galeorhinus galeusx; this collection includes all species belonging to these families which have previously and reliably been recorded from New Zealand waters, and of which adequate descriptions exist. The similarities of the cephalic appendages of caligoid copepods to those of free living copepods is discussed. The biogeographical relationships of the species here recorded are considered and it is concluded that many of these species, particularly those parasitic on elasmobranchs, are widespread, and that many of those with apparently restricted distributions may become known from other regions, especially when the little investigated parasite faunas of fishes from the South Pacific and South Atlantic become more fully known; the hosts from which the present species have been recorded are compared; it is shown that species occurring on elasmobranchs are confined to this but show little host specificity within it; teleost parasites may be restricted to one host species, one host genus, one host family, or to host families with systematic or ecological affinities; Cecrops latreillii is unique among these parasites in occurring on three quite different and apparently unrelated host species.</p>

Some Copepoda Parasitic on Fishes of the New Zealand Region

<p>Material representing 38 species of parasitic Copepoda, Order Caligoida, from New Zealand marine fishes, belonging to 20 genera and six families is discussed. Except for Lepeophtheirus erecsoni Thomson, of which only damaged material was available, the species are described and figured in detail. Previous records from New Zealand waters are discussed. The name Caligus vicarius is proposed for C. longicaudatus Brady which is preoccupied. Species examined and their hosts are as follows (new hosts for previously known species, and previously known species newly recorded from New Zealand are marked with asterisks) - Caligidae: Caligus brevis Shiinox on Pseudolabrus pittensisx, P. milesx and P. celidotusx; C. aesopus Wilsonx on Seriola grandisx; C. pelamydis Kroyerx on Thyrsites atunx; C. buechlerae Hewitt on Tripterygion sp.; Lepeophtheirus erecsoni Thomson on Latridopsis ciliaris; L. scutiger Shiinox on Pseudolabrus pittensisx, P. milesx and P. celidotusx; L. insignis Wilsonx on Mola mola; L. polyprioni Hewitt on Polyprion oxygenios and P. moeone; L. argentus Hewitt on Hyperoglyphe porosa; L. heegaardi Hewitt on Lepidopus caudatus; L. distinctus Hewitt on Genypterus blacodes; Euyphoridae: Gloiopotes huttoni (Thomson) on Makaira mitsukurii and M. marlina; Elytrophora brachyptera Gerstaekerx on Thunnus alalunga and. T. maccoyix; Pandaridae: Nesippus orientalis Hellerx on Mustelus antarcticus and Notorhynchus pectorosusx; N. borealis (Steenstrup and Lutken)x on Isurus oxyrinchusx; Dinemoura latifolia Steenstrup and Lutken on Carcharodon carcharias, Isurus oxyrinchus and Galeorhinus australis; D. producta (Muller) on Cetorhinus maximus and Carcharodon carcharias; Demoleus latus Shiinox on Squalus acanthiasx; Echthrogaleus braccatus (Dana) on an unrecorded host; E. coleoptratus (Guerin)x on Prionace glauca and Lamna nasus; E. denticulatus Smith on an unrecorded host; Phyllothyreus cornutus (Milne-Edwards)x on Isurus oxyrinchus; Pandarus bicolor Leachx on Squalus acanthias, Galeorhinus australisx, Notorhynchus pectorosusx and Cyprimulus sp.x; P. cranchii Leach on Galeorhinus australisx and Isurus oxyrinchus; Perissopus dentatus Steenstrup and Lutkenx on a hammerhead shark; Cecropidae: Cecrops latreillii Leach on Mola mola; Eudactylinidae: Nemesis lamna Rissox on Carcharodon carcharias, Cetorhinus maximus and Isurus oxyrinchus; N. robusta (van Beneden)x on Alopias vulpinus; Congericola pallidus van Benedenx on Conger vereauxix Dichelesthiidae; Pseudocycnus appendiculatus Hellerx on Thunnus alalunga; a new species of Hatschekia on Allomycterus jaculiferus; a further new species of Hatschekia on Lepidopus caudatus; Anthosomidae: a new species of Pseudolernanthropus on Thyrsites atun and Jordanidia solandri; a new species of Lernanthropus on Seriolella brama; Aethon percis (Thomson) on Parapercis coelias; two new species of Aethon on Cheilodactylus macropterus and Latridopus caudatues; Anthosoma crassum (Abildgaard) on Carcharodon carcharias, Isurus oxyrinchus, Lamna nasus and Galeorhinus galeusx; this collection includes all species belonging to these families which have previously and reliably been recorded from New Zealand waters, and of which adequate descriptions exist. The similarities of the cephalic appendages of caligoid copepods to those of free living copepods is discussed. The biogeographical relationships of the species here recorded are considered and it is concluded that many of these species, particularly those parasitic on elasmobranchs, are widespread, and that many of those with apparently restricted distributions may become known from other regions, especially when the little investigated parasite faunas of fishes from the South Pacific and South Atlantic become more fully known; the hosts from which the present species have been recorded are compared; it is shown that species occurring on elasmobranchs are confined to this but show little host specificity within it; teleost parasites may be restricted to one host species, one host genus, one host family, or to host families with systematic or ecological affinities; Cecrops latreillii is unique among these parasites in occurring on three quite different and apparently unrelated host species.</p>

Unique iris and pupil morphology in lamnid sharks

Documentation of the iris concentrating on color, pupillary shape, and orientation has been reported in a number of elasmobranch species, but has not been documented in lamnid sharks. This study examined the eyes of three lamnid sharks, white shark (Carcharodon carcharias), mako shark (Isurus oxyrinchus), and porbeagle shark (Lamna nasus) to characterize the iris color and pupil shape. All three species possess a brown color iris circling a horizontal slit pupil. A blue limbal ring of color circles the iris caused by the sclera and cartilage from the limbus which extends into the anterior chamber of the eye. The unique characteristics of the iris and pupil shape are described and implications of these findings on future research are discussed.

Non-random Co-occurrence of Juvenile White Sharks (Carcharodon carcharias) at Seasonal Aggregation Sites in Southern California

Many terrestrial and aquatic taxa are known to form periodic aggregations, whether across life history or solely during specific life stages, that are generally governed by the availability and distribution of resources. Associations between individuals during such aggregation events are considered random and not driven by social attraction or underlying community structure. White sharks (Carcharodon carcharias) have been described as a species that exhibits resource-driven aggregative behaviors across ontogenetic stages and juvenile white sharks are known to form aggregations at specific nursery sites where individuals may remain for extended periods of time in the presence of other individuals. We hypothesized juvenile white sharks form distinct communities during these critical early phases of ontogeny and discuss how a tendency to co-occur across life stages may be seeded by the formation of these communities in early ontogeny. We present results from a series of social network analyses of 86 juvenile white sharks derived from 6 years of passive acoustic telemetry data in southern California, demonstrating the likelihood of association of tagged juvenile white sharks is greater when sharks are of similar size-classes. Individuals in observed networks exhibited behaviors that best approximated fission-fusion dynamics with spatiotemporally unstable group membership. These results provide evidence of possible non-resource driven co-occurrence and community structure in juvenile white sharks during early life stages.

Seasonal occurrence and sexual segregation of great white sharks Carcharodon carcharias in Mossel Bay, South Africa

The seasonal occurrence and temporal sexual segregation of great white sharks Carcharodon carcharias have been widely documented in various temperate and sub-tropical waters across the globe. Yet, there is limited understanding of the relationship between the life stages and habitat use of C. carcharias, particularly in the Southern Cape. In this study, we investigated the population dynamics of C. carcharias in Mossel Bay, South Africa, between 2009 and 2013, using skipper logbooks and citizen research data obtained by a cage-diving vessel. A total of 3064 sharks, ranging in life history stages from young-of-the-year to subadult, were sighted during 573 trips. Juveniles dominated the sightings throughout the study, and there was marked sexual segregation, with females dominating the total sightings of sharks. C. carcharias were most abundant during the cooler, winter season, with females differing in abundance seasonally and males maintaining a low abundance throughout the year but peaking in the winter. In addition, sea surface temperature was the best indicator of C. carcharias presence. Abundance was greatest when vertical water visibility exceeded 3 m, with cloud cover influencing overall abundance negatively. Likely reasoning for the aggregation of C. carcharias in Mossel Bay includes the favourable conditions and abundance of food. Juvenile sharks may also utilise this area as a training ground to learn from larger conspecifics. This research demonstrates that information on population size and structure of C. carcharias can be obtained effectively through a compilation of logbook and citizen science data to assess and identify potential critical habitats in the quest to develop appropriate management strategies. This research also shows value in commercial cage-diving operations deriving international data sets needed to assess global populations of C. carcharias.

Three-Dimensional Movements and Habitat Selection of Young White Sharks (Carcharodon carcharias) Across a Temperate Continental Shelf Ecosystem

As highly mobile predators with extensive home ranges, some shark species often utilize a continuum of habitats across the continental shelf ranging from the surf zone to the open ocean. For many species, these cross-shelf distributions can change depending on ontogeny or seasonal conditions. Recent research has confirmed a white shark (Carcharodon carcharias) summer nursery off Long Island, New York; however, habitat characterization of this nursery has not yet been conducted nor has fine-scale analysis of vertical behavior. Between 2016 and 2019, 21 young-of-the-year and juvenile white sharks were fitted with satellite and acoustic tags to examine distribution and selection for a suite of oceanographic variables during their late summertime (i.e., August to October) residence in the New York Bight. Horizontal position estimates were used to extract a suite of environmental measurements via remote sensing platforms and were linked with vertical profiles to produce three-dimensional movements for a subset of individuals also fitted with pop-up satellite archival tags (n = 7). Sharks exhibited horizontal movements parallel to Long Island’s southern shoreline and coastal New Jersey, with distances from 0.1 to 131.5 km from shore. Log-likelihood chi-square analyses determined selection for waters with underlying bathymetry of 20–30 m, sea surface temperatures between 20.0 and 22.0°C, sea surface salinities between 31.0 and 32.0 ppt, and chlorophyll-a concentrations between 2.0 and 8.0 mg⋅m–3. Multiple individuals also traversed the mid- to outer shelf region after leaving the Montauk tagging area. Vertical depth profiles illustrated oscillations between the surface and 199 m of water, with an average swimming depth of 9.2 ± 8.9 m. Water column temperatures during these oscillations ranged between 7.9 and 26.2°C (mean = 19.5 ± 2.0°C) with several individuals traversing highly stratified regions presumably associated with a mid-shelf cold pool adjacent to the Hudson Shelf Valley. These results suggest young white sharks exhibit connectivity between the immediate shoreline and mid-continental shelf region, where they play important ecological roles as predators on a variety of species. Our study improves characterization of essential fish habitat for young white sharks and provides new insights into their reliance on this productive continental shelf ecosystem.