Authors in bold are/were staff of the Institute for Ocean Conservation Science and its founding organization, the Pew Institute for Ocean Science
Babcock, E.A., McAllister, M.K., E.K. Pikitch. 2007. Comparison of Harvest Control Policies for Rebuilding Overfished Populations within a Fixed Rebuilding Time Frame. North American Journal of Fisheries Management. 27:1326-1342. -
U.S. law requires that overfished fish populations be rebuilt within 10 years when biologically possible, and otherwise within the time it would take to rebuild in the absence of fishing plus one mean generation time (MGT). Most overfished populations can recover in less than 10 years; the exceptions are populations with very low productivity and some that are severely depleted. A range of harvest control policies, including constant fishing mortalities and variable harvest rate control rules, were compared in terms of their ability to rebuild overfished populations of five species within the required times. The North Atlantic swordfish Xiphias gladius and Gulf of Mexico red snapper Lutjanus campechanus populations were able to rebuild in 10 years, but the white marlin Tetrapturus albidus, sandbar shark Carcharhinus plumbeus, and darkblotched rockfish Sebastes crameri populations were not. The harvest policy that resulted in populations being rebuilt most rapidly was either a control rule that reduced fishing mortality with decreasing biomass or a constant harvest rate designed to meet the current rebuilding time requirement. The control rules we analyzed restricted catches at the beginning of the rebuilding period but allowed catches to increase rapidly as the population was rebuilt. Thus, there was a trade-off between relatively high catches early in the rebuilding period and high catches later in the rebuilding period when the population had been rebuilt and could sustain high catches. Whether the population was rebuilt more rapidly under a fixed rebuilding-time requirement or a control rule depended on the productivity of the population.
Received: April 26, 2006; Accepted: April 2, 2007; Published Online: November 15, 2007
North American Journal of Fisheries Management 2007;27:1326–1342
* Corresponding author: firstname.lastname@example.org
Becker, B.H., Peery, M., Beissinger, S.R.. 2007. Ocean climate and prey availability affect the reproductive success of an endangered seabird, the marbled murrelet. Marine Ecology Progress Series. 329:267-279.
Chapman, D. D., Shivji, M. S., Louis, E., Sommer, J., Fletcher, H., P. A. Prodöhl. 2007. Virgin birth in a hammerhead shark. Biology Letters. 10.1098/rsbl.2007.01.
Parthenogenesis has been documented in all major jawed vertebrate lineages except mammals and cartilaginous fishes (class Chondrichthyes: sharks, batoids and chimeras). Reports of captive female sharks giving birth despite being held in the extended absence of males have generally been ascribed to prior matings coupled with long-term sperm storage by the females. Here, we provide the first genetic evidence for chondrichthyan parthenogenesis, involving a hammerhead shark (Sphyrna tiburo). This finding also broadens the known occurrence of a specific type of asexual development (automictic parthenogenesis) among vertebrates, extending recently raised concerns about the potential negative effect of this type of facultative parthenogenesis on the genetic diversity of threatened vertebrate species.
Chapman, D. D., Pikitch, E. K., Babcock, E. A., M. Shivji. 2007. Deep-diving and diel changes in vertical habitat use by Caribbean reef sharks Carcharhinus perezi. Marine Ecology Progress Series. Vol. 344: 271–275.
Longline sampling (83 sets) supplemented with 6 pop-off archival transmitting (PAT) tag deployments were used to characterize vertical habitat use by Caribbean reef sharks Carcharhinus perezi at Glover’s Reef atoll, Belize. Longline catch-per-unit-effort (CPUE) in 2 shallow reef habitats (lagoon <18 m depth, fore-reef <40 m depth) underwent significant nocturnal increases for sharks larger than 110 cm total length (TL), but not for smaller sharks. Nocturnal CPUE of small sharks appeared to increase in the lagoon and decrease on the fore-reef, suggestive of movements to avoid larger conspecifics. PAT tag deployments (7 to 20 d) indicate that large C. perezi generally increased the amount of time they spent in the upper 40 m of the water column during the night, and inhabited much greater depths and tolerated lower temperatures than previously described. The wide vertical (0 to 356 m) and temperature range (31 to 12.4°C) documented for this top-predator reveals ecological coupling of deep and shallow reef habitats and has implications for Marine Protected Area (MPA)design.
KEY WORDS: Satellite tracking · Depth range · Coral reef ecology · Marine Protected Area · Carcharhinidae
Source: Marine Ecology Progress Series
Doukakis P., Jonahson M., Ramahery V., Randriamanantsoa B.J.D. . 2007. Traditional fisheries of Antongil Bay, Madagascar. Western Indian Ocean J. of Marine Science . 6(2): 175-181.
Erickson, D. L., Kappenman, K., Webb, M., Ryabinin, N., Shmigirilov, A., Belyaev, B., Novomodny, G., Mednikova, A., Pikitch, E., P. Doukakis. 2007. Sturgeon Conservation in the Russian Far East and China. Endangered Species Bulletin. September: 28-32.
Endangered Species Bulletin
Erickson, D. L., J. E. Hightower. 2007. Oceanic Distribution and Behavior of Green Sturgeon. American Fisheries Society Symposium. 56:197-211.
Acipenser medirostris off the U.S. and Canadian west coasts. Seven green sturgeon were tagged with PATs in the Rogue River, Oregon, during the autumn months of 2001 and 2002. All fish left the Rogue River and entered the ocean within 32 d of tagging. Six of seven tags popped off and transmitted data to satellites, as planned, 2.5 to 7.7 months after the fish left the Rogue River. One tag detached prematurely 5.7 months after tagging, but it drifted ashore in northern Oregon and was returned.
All PAT-tagged sturgeon migrated north of the Rogue River after entering the ocean; pop-off locations ranged from the central Oregon coast to northwestern Vancouver Island, Canada. Estimated distances migrated through nearshore waters ranged from 221 to 968 km. Potential concentration sites off the Oregon and Washington coasts were identified using PAT and Oregon trawl logbook data sets. Green sturgeon exhibited a narrow and shallow depth distribution (typically < 100 m) over the continental shelf. This limited depth distribution makes green sturgeon vulnerable to trawl bycatch in the open ocean, which will increase if trawling within the narrow depth range increases.
Although green sturgeon with PATs typically occupied depths of 40–70 m, they also occasionally made what appeared to be rapid vertical ascents to or near the surface. Green sturgeon tagged with PATs often were more active and occupied shallower depths at night than during the day. Green sturgeon are harvested by commercial, treaty, and sport fisheries. Because the population trends and abundance of green sturgeon are uncertain, and because green sturgeon from the main spawning rivers are probably mixed along the U.S. West Coast, conservative management measures should be implemented throughout the species’ range to limit fishing mortality and ensure effective conservation.
Erickson, D.L., Webb, M.A.H.. 2007. Spawning Periodicity, Spawning Migration, and Size at Maturity of Green Sturgeon (Acipenser medirostris) in the Rogue River, Oregon. Environmental Biology of Fishes. 79:255-268.
Pop-off archival tags (PATs) and trawl logbook data were used to study the distribution, movement, and behavior of green sturgeon The Rogue River, Oregon represents one of three important spawning systems for green sturgeon, Acipenser medirostris, in North America. In this paper we describe the spawning migration, spawning periodicity, and size at maturity for green sturgeon caught in the Rogue River during 2000–2004. Green sturgeon were caught by gill net or angling; 103 individuals were tagged with radio or sonic transmitters (externally or internally). Green sturgeon caught by gill net and angling ranged from 145 cm to 225 cm total length. Histological and visual examinations of gonad tissues indicated that most green sturgeon were spawning or post-spawning adults that entered the Rogue River to spawn. Ripe individuals were caught when water temperature was 10–18°C. Specimens carrying transmitters migrated 17–105 km up river; reaches consisting of likely spawning sites were identified based on sturgeon migratory behavior. Most green sturgeon remained in the Rogue River until late fall or early winter when flows increased, after which they returned to the ocean. Eight green sturgeon (males and females) returned to the Rogue River 2–4 years after leaving, entering the river during March, April, and May when water temperatures ranged from 9°C to 16°C. None of the 103-tagged individuals entered the Rogue River during successive years. There appear to be few known natural threats to adult green sturgeon in the Rogue River. However, our data suggest that a high percentage of adults that spawn in the Rogue River (particularly males) were susceptible to harvest by commercial, Tribal, and sport fisheries after leaving the system because they were not adequately protected by maximum size limits during the period of this study. The implications of maximum size limits (or lack of size limits) to green sturgeon are discussed, and recent actions taken by Oregon and Washington Fish and Wildlife Commissions to manage green sturgeon more conservatively are presented.
Keywords Telemetry - Size limit - Flow - Temperature - Spawning interval - Fidelity
Magnussen J E, Pikitch E K, Clarke S C, Nicholson C, Hoelzel A R, Shivji M. 2007. Genetic tracking of basking shark products in international trade. Online Early Publications. Animal Conservation.
Myers, R A, Baum J K, Shepherd T D, Powers S P, Peterson C H. 2007. Cascading Effects of the loss of apex predatory sharks from a coastal ocean. Science. 315 (5820):1846-1850.
Webb, M.A.H., Erickson, D.L.. 2007. Reproductive structure of the adult green sturgeon (Acipenser medirostris) in the Rogue River, Oregon. Environmental Biology of Fishes. 79:305-314.
The primary objective of this study was to determine the reproductive structure of the adult green sturgeon population in the Rogue River. Green sturgeon were captured by gillnet in the lower 11.6–68.4 river kilometers in April to July 2000–2003 and September and October 2002–2003. Gonadal tissue, collected by biopsy, was processed histologically, blood was collected from the caudal vasculature, and fork length (FL) and total length (TL) (±0.5 cm) were measured for each individual. Sex steroids, testosterone (T), 11-ketotestosterone (11-KT), and estradiol-17β (E2), were measured by radioimmunoassay. Biological samples were collected from a total of 88 green sturgeon of which 37 females and 41 males were confirmed by histological analysis. Four gravid females, captured in the spring, were visually identified, and oocyte polarization index and ovarian follicle diameter indicated that these females were in spawning condition. Gonadal samples collected from six individuals did not contain gonial cells, hence the sex and stage of maturity in these individuals remains unknown. Of the 20 females captured in the spring, 1 was vitellogenic, 4 were post-vitellogenic, and 15 were post-ovulatory. Twenty-one females were captured in the fall of which 6 were pre-vitellogenic, 7 vitellogenic, and 8 post-ovulatory. Of the 16 males captured in the spring, 2 were pre-meiotic, 8 were ripe or actively spermiating, and 6 were post-spermiation. Twenty-five males were captured in the fall: 11 pre-meiotic males and 14 post-spermiation. The majority of green sturgeon captured in the Rogue River were reproductively active or had recently spawned indicating the importance of this river for the preservation of green sturgeon.
Keywords Green sturgeon - Reproduction - Rogue River
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