Daryl Parkyn

Falkland Islands Fisheries Department

The lack of data on the age, growth, and reproduction of the Atlantic Goliath Grouper Epinephelus itajara off the coasts of Florida (USA) makes it difficult to estimate the extent of their population recovery following the 1990 fishery closure, as well as the potential effects of the recent (2023) opening of a fishery for juveniles. Goliath Grouper...

Two nektonic squid species, Illex argentinus in the Southwest Atlantic and Dosidicus gigas in the Eastern Pacific, are amongst the largest commercial cephalopod resources; presently comprising from one third to almost one half of the global cephalopod catch. These squids are straddling stocks exploited during their ontogenetic migrations both withi...

Species delimitation is a major quest in biology and is essential for adequate management of the organismal diversity. A challenging example comprises the fish species of red snappers in the Western Atlantic. Red snappers have been traditionally recognized as two separate species based on morphology: Lutjanus campechanus (northern red snapper) and...

Skip main navigationJournal menuClose Drawer Menu MoreSections Restricted accessResearch articles Genomics overrules mitochondrial DNA, siding with morphology on a controversial case of species delimitation Carmen del R. Pedraza-Marrón , Raimundo Silva , Jonathan Deeds , Steven M. Van Belleghem , Alicia Mastretta-Yanes , Omar Domín...

The US Gulf of Mexico stock assessment of greater amberjack Seriola dumerili assumes a 1:1 male:female sex ratio. However, the observed sex ratio in the landed catch is 1:1.8, and for fish >1 m fork length is 1:2.4. To theoretically explore whether this female-skewed sex ratio may arise due to differential fishing mortality between the sexes, we us...

The greater amberjack (Seriola dumerili) is a commercially and recreationally important marine fish species in the southeastern United States, where it has been historically managed as two non-mixing stocks (Gulf of Mexico and Atlantic). Mark-recapture studies and analysis of mitochondrial DNA have suggested the two stocks are demographically indep...

Parasites account for over half of the biodiversity on coral reefs, yet their ecological impacts are poorly understood. Cymothoid isopods of the genus Anilocra are large, conspicuous ectoparasites of coral reef fishes. French grunt (Haemulon flavolineatum) and brown chromis (Chromis multilineata) are commonly infected by Anilocra spp. in the Caribb...

The effect of solid-body blocking in a large (257 l) Blazka-style respirometer was examined in gag Mycteroperca microlepis. Gag ranging from 376-690 mm total length were tested at velocities from 10 to 91 cm s-1. The solid blocking effect (SBE) due to fish size, swimming speed, and water temperature was investigated by direct measurement of flow ve...

Stock assessments for the Gulf of Mexico (Gulf) Greater Amberjack Seriola dumerili continue to designate the stock as overfished and undergoing overfishing, despite increasing regulatory measures. Knowledge of sex-specific spatial distribution and fishing mortality may contribute to our understanding of the stock’s overexploitation, especially sinc...

Goliath Grouper Epinephelus itajara is currently listed globally as “critically endangered” and has been protected from both commercial and recreational fishing in U.S. waters since 1990; virtually all of the goliath grouper catch in the U.S. was landed in Florida. Recently there has been interest expressed by fishers to re-open a limited-type of h...

Uv cones mechanisms besides directly involved in color vision, extending the range of the wavelengths and intensity in which color discrimination can be done (Hawryshyn et al.,, contributing to visually guide the search, detection and capture of prey, especially zooplankton, increased their contrast in surface waters rich in ultraviolet light Deuts...

Bull Sharks Carcharhinus leucas in the Indian River Lagoon, Florida, have been documented to frequently occur in human‐altered habitats, including dredged creeks and channels, boat marinas, and power plant outfalls. The purpose of this study was to examine the short‐term movements of age‐0 and juvenile Bull Sharks to quantify the extent to which th...

Gulf of Mexico greater amberjack Seriola dumerili have been designated as currently overfished and undergoing overfishing. Release mortality rates for amberjack in the Gulf of Mexico are unknown, yet releases are projected to increase as regulations become more restrictive. In this study, 1,493 amberjack were tagged and released to estimate release...

Greater amberjack Seriola dumerili in the eastern United States are currently managed as two distinct stocks, with one stock residing in the Gulf of Mexico and a second along the Atlantic Coast (including the Florida Keys). Support for independent management of the two stocks is based on both tagging and molecular data. Current management assumes m...

The most recent stock assessment for Gulf of Mexico greater amberjack Seriola dumerili found it to be overfished and undergoing overfishing. Sex-specific spatial distribution and exploitation may be important for greater amberjack because of sex‑specific mortality due to minimum size limits and possible regional skewing of sex ratios. Being able to...

Accurate data on fish diets play a fundamental role in understanding trophic interactions and help explain habitat-use patterns and nutrient flow between systems. In the present study, the diet of a reef fish was characterised by visual identification and augmented with an alternative, non-visual-based method of diet analysis to generate identifica...

Trophic linkages within a coral-reef ecosystem may be difficult to discern in fish species that reside on, but do not forage on, coral reefs. Furthermore, dietary analysis of fish can be difficult in situations where prey is thoroughly macerated, resulting in many visually unrecognisable food items. The present study examined whether the inclusion...

Greater amberjack Seriola dumerili in the Gulf of Mexico are overfished, yet their population dynamics are still poorly understood and age and growth over most of its exploitation range is unknown. In cooperation with state and federal fisheries agencies in the southeastern U.S., a total of 1,838 fish from 74 to 1829 mm fork length were collected d...

Greater amberjack, Seriola dumerili, is a pelagic reef fish that is managed in the US as two separate stocks, the Gulf and the Atlantic. The most recent stock assessment for the Gulf stock found it to be overfished and undergoing overfishing. Sex-specific spatial distribution and exploitation may contribute to our understanding of the stock’s overe...

Yellow bullhead (Ictaluridae: Ameiurus natalis) is the most abundant ictalurid catfish in the Everglades of southern Florida, USA, and, as both prey and predator, is one of many essential components in the ecological-simulation models used in assessing restoration success in the Everglades. Little is known of its biology and life history in this so...

Abstract  Florida gar, Lepisosteus platyrhincus DeKay, were sampled in two canal systems in south Florida during 2000–2001 to estimate age, growth and mortality as part of the Everglades ecosystem-restoration effort. Tamiami (C-4) and L-31W canal systems had direct connections to natural wetlands of the Everglades and harboured large Florida gar po...

Currently, there is a conflict between the need to conserve protected fish species and the need to use lethal methods to collect essential biological data, such as age, to assess their population status and recovery trends. We evaluated the precision and accuracy of a non-lethal ageing method for goliath grouper Epinephelus itajara, listed as criti...

Currently, there is a conflict between the need to conserve protected fish species and the need to use lethal methods to collect essential biological data, such as age, to assess their population status and recovery trends. We evaluated the precision and accuracy of a non-lethal ageing method for goliath grouper Epinephelus itajara, listed as criti...

Post-release survival and upstream movement of Gulf of Mexico sturgeon (Acipenser oxyrinchus desotoi) in the Suwannee River, Florida, were examined following induced spawning using carp pituitary extract (CPE). Six mature females (one CPE-treated and five control) and 12 mature males (five CPE-treated and seven control) were implanted with ultrason...

The distribution of threatened Gulf of Mexico sturgeon Acipenser oxyrinchus desotoi (hereafter referred to as Gulf sturgeon) in the Suwannee River estuary, Florida, was examined relative to the distribution of benthic invertebrate prey and environmental variables (salinity, temperature, dissolved oxygen, and sediment type) to determine potential fo...

Sex-specific age and growth were determined for white grunt, Haemulon plumieri (Lacepède, 1801), from their main fishing area on the Gulf coast of Florida. In total, 4043 fish were collected using hook-and-line or trap gear: 2617 from the central and 1426 from the north-central Gulf coast of Florida. White grunt were aged reliably using thin-sectio...

Rates of loss of juvenile red drum Sciaenops ocellatus (∼85 mm total length) stocked out of season were estimated using hatchery releases and ultrasonically tagged fish in Pumpkin and May creeks in the Chassahowitzka National Wildlife Refuge on the Gulf coast of Florida. In Pumpkin Creek, approximately 7,000 of the 10,000 fish released on 27 June 2...

We examined orientation responses of juvenile salmonids to a polarized-light stimulus under laboratory conditions. Juvenile rainbow trout, Oncorhynchus mykiss, steelhead (anadromous), O. mykiss, and brook char, Salvelinus fontinalis, were trained using an operant conditioning methodology to orient relative to the axis of a linear-polarized light fi...

White grunts Haemulon plumieri were sampled from catches of the headboat fishery operating on the Gulf Coast of Florida to determine sex-specific total mortality by using catch curve analyses. Sampling was conducted during the peak of the spawning season (April-June) and in a postspawning season (July-October). In total, 1,051 white grunts were sam...

Juvenile red drum (Sciaenops ocellatus), reared in either 15- or 30-ppt salinity seawater, were tested to determine whether they develop preference for the salinity of the water in which they were cultured. In a two-choice test, large- and small-sized juvenile red drum chose the raceway that matched the seawater in which they were cultured over the...

Spectral and polarisation sensitivity were compared among juvenile (parr) rainbow trout (Oncorhynchus mykiss), steelhead (O. mykiss), cutthroat trout (O. clarki clarki), kokanee (O. nerka) and brook char (Salvelinus fontinalis) using multi-unit recording from the optic nerve. Although reared under the same conditions, differences in photopic spectr...

Juvenile rainbow trout (Oncorhynchus mykiss) were given ethambutol (900 mg kg-1 body mass per day) for 4 weeks to examine its effects on vision. Using multi-unit recording from the optic nerve, spectral sensitivity of the on-responses were significantly affected in two regions, 340-440 nm and 600-660 nm. Off-responses were statistically unaffected....

The distribution and activities of rockfish, Sebastes spp., inhabiting depths between 21 and 150 m in the coastal fjord of Saanich Inlet, British Columbia, were assessed byusing the Pisces IV submersible. Quillback rockfish,S.maliger, was the numerically dominant rockfish, attaining a median density of 5.7 fish·l00m-2 between 21 m and 100 m of dept...

Integrated spike activity of axons from the optic nerve was measured in an investigation of the e-vector sensitive mechanism underlying the ability of rainbow trout (Oncorhynchus mykiss) for orientation in downwelling, linearly-polarized light. In anaesthetized, immobilized fish, one eye was exposed to incremental light flashes which were superimpo...

Thesis (Ph. D.)--University of Victoria, 1998. Includes bibliographical references.