National Oceanic and Atmospheric Administration
Coastal Services Center Technical Report, NOAA/CSC/99031-PUB/001
Two airborne light detection and ranging (LIDAR) beach surveys of the North Carolina coast are used to assess the hurricane-induced impacts from Hurricane Bonnie. The baseline survey was conducted over North Carolina in fall of 1997, and a second survey was conducted in fall of 1998, within days of Bonnie's landfall. The very high density and accuracy of elevation measurements allows regional-scale beach volume calculations at an accuracy unavailable using traditional beach profiling survey methods. Geographic information system software is used to determine volumetric change of the dry beach for all North Carolina barrier beaches. From volumetric change calculations, the volume of sediment gain or loss by unit area and unit length of the beach are determined for each beach. The northern barrier island beaches show greater average sediment loss over the length of the beach than the beaches in the middle and southern sections of the coast. The northern beaches generally show long erosio...
A baseline assessment of 36 economically and ecologically important Florida Keys reef fish stocks is provided using a systems approach that integrates sampling, statistics, and mathematical modeling. Quantitative fishery-independent data from reef fish visual surveys conducted by SCUBA divers from 1979 to 1996 were used to develop estimates of population abundance, assemblage composition, and stock structures in relation to key physical and habitat factors. Exploitation effects were assessed with a new length-based algorithm that calculates total mortality rates from estimates of "average length of frish in the exploitable phase of the stock." These estimates were highly correlated for two statistically independent data sources on reef fish: fishery-independent diver observations and fishery-dependent head boat catches. We developed a reef fish equilibrium exploitation fishery simulation (REEFS) model and used estimates of fishing mortality to assess yield-per-recruit in relation to fishing intensity and gear selectivity and to assess spawning potential ratio (SPR) in relation to U.S. federal "overfishing" standards. Our analyses show that 13 of 16 groupers (Epinephelinae), 7 of 13 snappers (Lutjanidae), one wrasse (Labridae), and 2 of 5 grunts (Haemulidae) are below the the 30% SPR overfishing minimum. Some stocks appear to have been chronically overfished since the late 1970s. The Florida Keys reef fishery exhibits classic "serial overfishing" in which the largest , most desirable, and vulnerable species are depleted by fishing. Rapid growth of the barracuda population (Sphyraenidae) during the same period suggests that fishing has contributed to substantial changes in community structure and dynamics.
The usually enriched belt which corresponds to the equatorial upwelling vanished after September 1982, except for a reduced zone east of long. 120oW, where a moderate enrichment persisted throughout the warm event. It recovered after July 1983, spreading westwards to long. 170oE. During the mature phase of El Nino (October 1982-June 1983), an enriched zone appeared in the W Pacific, centered at c7oN, consistent with a rise of the thermocline in this region. An examination of oceanographic data collected in this region since 1970 shows that nutrients from below the thermocline are consumed by the phytoplankton during each El Nino. This W Pacific enrichment was weakened with time, and the period from April to June 1983 was characterized by low sea surface chlorophyll concentration (SSCC) values over most of the tropical Pacific. Unusually high SSCC values are reported in subtropical zones, during the austral winters of 1982 and 1983 in the SW Pacific and during the 1982 autumn in the NE Pacific, which may be due to advection of rich water from higher latitudes and to intensified vertical mixing by strong westerly winds, respectively.-from Author
"Catch rates for the 13 most abundant species caught in the deep-set Hawaii-based longline fishery over the past decade (1996–2006) provide evidence of a change among the top North Pacific subtropical predators. Catch rates for apex predators such as blue shark (Prionace glauca), bigeye (Thunnus obesus) and albacore (Thunnus alalunga) tunas, shortbill spearfish (Tetrapturus angustirostris), and striped marlin (Tetrapturus audax) declined by 3% to 9% per year and catch rates for four midtrophic species, mahimahi (Coryphaena hippurus), sickle pomfret (Taractichthys steindachneri), escolar (Lepidocybium flavobrunneum), and snake mackerel (Gempylus serpens), increased by 6% to 18% per year. The mean trophic level of the catch for these 13 species declined 5%, from 3.85 to 3.66. A shift in the ecosystem to an increase in midtrophic-level, fast-growing and short-lived species is indicated by the decline in apex predators in the catch (from 70% to 40%) and the increase in species with production to biomass values of 1.0 or larger in the catch (from 20% to 40%). This altered ecosystem may exhibit more temporal variation in response to climate variability."
"Groundfish fisheries in the southeast Bering Sea in Alaska have been constrained in recent years by management measures to protect the endangered Steller sea lion (Eumetopias jubatus). There is concern that the present commercial harvest may produce a localized depletion of groundfish that would affect the foraging success of Steller sea lions or other predators. A threeyear field experiment was conducted to determine whether an intensive trawl fishery in the southeast Bering Sea created a localized depletion in the abundance of Pacific cod (Gadus macrocephalus). This experiment produced strongly negative results; no difference was found in the rate of seasonal change in Pacific cod abundance between stations within a regulatory no-trawl zone and stations in an immediately adjacent trawled area. Corollary studies showed that Pacific cod in the study area were highly mobile and indicated that the geographic scale of Pacific cod movement was larger than the spatial scale used as the basis for current no-trawl zones. The idea of localized depletion is strongly dependent on assumed spatial and temporal scales and contains an implicit assumption that there is a closed local population. The scale of movement of target organisms is critical in determining regional effects of fishery removals."
The size-frequency distribution of the commercial catch is often used as the basis of fisheries stock assessments (Paul and Morgan, 1987; Gulland and Rosenberg, 1992) because most dynamic processes of populations (growth, survival, recruitment) are reflected in changes in this distribution. The data are generally collected, often at great expense, by sampling the catch at landing sites and markets, or onboard fishing vessels.
Size-frequency distributions of prawns (Penaeus esculentus and P. semisulcatus) can also be obtained from fish processors, who grade landings by size. These data are easier and cheaper to obtain than research samples, but unfortunately they are also considered less accurate and lack spatial information. However, they have been used in stock assessment of prawns in Kuwait (Jones and van Zalinge, 1981) and Malaysia (Simpson and Kong, 1978).
It is often difficult to relate size data obtained from a processor to time and place of capture of the prawns, but this is not the case when the product is packed onboard, as in Australia's northern prawn fishery (NPF).
Trawler operators in the NPF have voluntarily recorded size composition since 1985, when provision for this was made in operators' daily logbooks (between 30% and 45% of the tiger prawn catch reported in the logbooks contain size information). These books are therefore the most comprehensive source of information on the spatial and temporal size distribution of the commercial catch of the NPF. Present assessments of the fishery are based on deterministic growth and deterministic seasonal recruitment patterns (Wang and Die, 1996) and do not use size-structured data. If available, these data would help relax the recruitment and improve current stock assessments of the NPF.
Before the size data recorded in the logbooks can be used, however, the accuracy of size grading at sea needs to the assessed. This paper examines the accuracy of grading tiger prawns, by using data collected from a private firm, A. Raptis and Sons, that operates a large modern processing factory that regularly assesses the onboard grading of product purchased from NPF trawler operators.
Although the work presented here relates specifically to the NPF, the practice of onboard size grading is widespread in other fisheries around the world. Therefore our methods have potential application to other fisheries.
During the VIITAL cruise in the Bay of Biscay in summer 2002, two devices for measuring the length of swimming fish were tested: 1) a mechanical crown that emitted a pair of parallel laser beams and that was mounted on the main camera and 2) an underwater auto-focus video camera. The precision and accuracy of these devices were compared and the various sources of measurement errors were estimated by repeatedly measuring fixed and mobile objects and live fish. It was found that fish mobility is the main source of error for these devices because they require that the objects to be measured are perpendicular to the field of vision. The best performance was obtained with the laser method where a video-replay of laser spots (projected on fish bodies) carrying real-time size information was used. The auto-focus system performed poorly because of a delay in obtaining focus and because of some technical problems.
This paper is not subject to U.S. copyright. The definitive version was published in Fishery Bulletin 107 (2009): 384–394. Although the Atlantic white-sided dolphin (Lagenorhynchus acutus) is one of the most common dolphins off New England, little has been documented about its diet in the western North Atlantic Ocean. Current federal protection of marine mammals limits the supply of animals for investigation to those incidentally caught in the nets of commercial fishermen with observers aboard. Stomachs of 62 L. acutus were examined; of these 62 individuals, 28 of them were caught by net and 34 were animals stranded on Cape Cod. Most of the net-caught L. acutus were from the deeper waters of the Gulf of Maine. A single stomach was from the continental slope south of Georges Bank. At least twenty-six fish species and three cephalopod species were eaten. The predominant prey were silver hake (Merluccius bilinearis), spoonarm octopus (Bathypolypus bairdii), and haddock (Melanogrammus aeglefinus). The stomach from a net-caught L. acutus on the continental slope contained 7750 otoliths of the Madeira lanternfish (Ceratoscopelus maderensis). Sand lances (Ammodytes spp.) were the most abundant (541 otoliths) species in the stomachs of stranded L. acutus. Seasonal variation in diet was indicated; pelagic Atlantic herring (Clupea harengus) was the most important prey in summer, but was rare in winter. The average length of fish prey was approximately 200 mm, and the average mantle length of cephalopod prey was approximately 50 mm.
Commercial and scientific bottom longline catches of alfonsino, #Beryx splendens$, from seamounts of New Caledonia were sampled to study length-frequency distributions. A total of 14,674 fish were measured. CPUE of #Beryx splendens$ on two seamounts is modelled in terms of length and depth. The data show that mean length increases with depth ; this is well described by a bivariate normal model that estimates catch for a given seamount. In addition, the data show that mean length also varies with the depth of the top of seamounts ; this is described by a recursive model that is designed to predict approximate catch for any seamount. The limitations of both models are discussed, particularly with regard to temporal variation. (Résumé d'auteur)
We propose a new equation to describe the relation between otolith length (OL) and somatic length (fork length [FL]) of fish for the entire lifespan of the fish. The equation was developed by applying a mathematical smoothing method based on an allometric equation with a constant term for walleye pollock (Theragra chalcogramma) —a species that shows an extended longevity (>20 years). The most appropriate equation for defining the relation between OL and FL was a four-phase allometric smoothing function with three inf lection points. The inf lection points correspond to the timing of settlement of walleye pollock, changes in sexual maturity, and direction of otolith growth. Allometric smoothing functions describing the relation between short otolith radius and FL, long otolith radius and FL, and FL and body weight were also developed. The proposed allometric smoothing functions cover the entire lifespan of walleye pollock. We term these equations "allometric smoothing functions for otolith and somatic growth over the lifespan of walleye pollock."
"The population structure and abundance of the American lobster (Homarus americanus) stock in the Gulf of Maine are defined by data derived from a fishery-independent trawl survey program conducted by the National Marine Fisheries Service (NMFS). Few sampling stations in the survey area are located inshore, in particular along coastal Maine. According to statistics, however, more than two thirds of the lobster landings come from inshore waters within three miles off the coast of Maine. In order to include an inshore survey program, complementary to the NMFS survey, the Maine Department of Marine Resources (DMR) initialized an inshore survey program in 2000. The survey was modeled on the NMFS survey program, making these two survey programs comparable. Using data from both survey programs, we evaluated the population structure of the American lobster in the Gulf of Maine. Our findings indicate that lobsters in the Gulf of Maine tend to have a size-dependent inshore-off-shore distribution; smaller lobsters are more likely to stay inshore and larger lobsters are more likely to stay offshore. The DMR inshore and NMFS survey programs focused on different areas in the Gulf of Maine."
This paper is not subject to U.S. copyright. The definitive version was published in Fishery Bulletin 106 (2008): 183-193. The identification of sea bass (Centropristis) larvae to species is difficult because of similar morphological characters, spawning times, and overlapping species ranges. Black sea bass (Centropristis striata) is an important fishery species and is currently considered to be overfished south of Cape Hatteras, North Carolina. We describe methods for identifying three species of sea bass larvae using polymerase chain reaction (PCR) and restriction fragment length polymorphism (RFLP) assays based on species-specific amplification of rDNA internal transcribed spacer reg ions. The assays were tested against DNA of ten other cooccurring reef fish species to ensure the assay’s specificity. Centropristis larvae were collected on three cruises during cross-shelf transects and were used to validate the assays. Seventysix Centropristis larvae were assayed and 69 (91%) were identified successfully. DNA was not amplified from 5% of the larvae and identification was inconclusive for 3% of the larvae. These assays can be used to identify sea bass eggs and larvae and will help to assess spawning locations, spawning times, and larval dispersal. Collection of larvae at sea was supported by funding from the National Science Foundation through OCE 9876565 to C. Jones, S. Thorrold, A. Valle-Levinson, and J. Hare. Additional funding for this project was provided by Office of National Marine Sanctuaries and by Grays Reef National Marine Sanctuary.
"For many fish stocks,resource management cannot be based on stock assessment because data are insufficient—a situation that requires alternative approaches to management. One possible approach is to manage data-limited stocks as part of an assemblage and to determine the status of the entire unit by a data-rich indicator species. The utility of this approach was evaluated in analyses of 15 years of commercial and 34 years of recreational logbook data from reef fisheries off the southeastern United States coast. Multivariate statistical analyses successfully revealed three primary assemblages. Within assemblages, however, there was little evidence of synchrony in population dynamics of member species,and thus, no support for the use of indicator species. Nonetheless, assemblages could prove useful as management units. Their identification offers opportunities for implementing management to address such ecological considerations as bycatch and species interrelations."
"Fish-habitat associations were examined at three spatial scales in Monterey Bay, California, to determine how benthic habitats and land- scape configuration have structured deepwater demersal fish assemblages. Fish counts and habitat variables were quantified by using observer and video data collected from a submersible. Fish responded to benthic habitats at scales ranging from cm’s to km’s. At broad-scales (km’s), habitat strata classified from acoustic maps were a strong predictor of fish assemblage composition. At intermediate-scales (m’s−100 m’s), fish species were associated with specific substratum patch types. At fine-scales (<1 m), micro-habitat associations revealed differing degrees of microhabitat specificity, and for some species revealed niche separation within patches. The use of habitat characteristics in ecosystem-based management, particularly as a surrogate for species distributions, will depend on resolving fish-habitat associations and habitat complexity over multiple scales."
This paper is not subject to U.S. copyright. The definitive version was published in Fishery Bulletin 107 (2009): 329-338. For most migratory fish, little is known about the location and size of foraging areas or how long individuals remain in foraging areas, even though these attributes may affect their growth, survival, and impact on local prey. We tested whether striped bass (Morone saxatilis Walbaum), found in Massachusetts in summer, were migratory, how long they stayed in non-natal estuaries, whether observed spatial patterns differed from random model predictions, whether fish returned to the same area across multiple years, and whether fishing effort could explain recapture patterns. Anchor tags were attached to striped bass that were caught and released in Massachusetts in 1999 and 2000, and recaptured between 1999 and 2007. In fall, tagged striped bass were caught south of where they were released in summer, confirming that fish were coastal migrants. In the first summer, 77% and 100% of the recaptured fish in the Great Marsh and along the Massachusetts coast, respectively, were caught in the same place where they were released. About two thirds of all fish recaptured near where they were released were caught 2–7 years after tagging. Our study shows that smaller (400–500 mm total length) striped bass migrate hundreds of kilometers along the Atlantic Ocean coast, cease their mobile lifestyle in summer when they use a relatively localized area for foraging (<20 km2), and return to these same foraging areas in subsequent years. This project was administered through the Massachusetts Cooperative Fish and Wildlife Research Unit. The Massachusetts Cooperative Fish and Wildlife Research Unit is an association among the U.S. Geological Survey; University of Massachusetts Department of Natural Resources Conservation; Massachusetts Division of Marine Fisheries; Massachusetts Division of Fisheries and Wildlife, and the Wildlife Management Institute.
Reprinted from Fishery Bulletin, Vol. 75 (1), pages 125-145. A 1½-yr survey of planktonic fish larvae collected from 2 to 111 km off the mid-Oregon coast in 1971-72 yielded 287 samples which contained 23,578 individuals in 90 taxonomic groups, 78 identified at the species level. Two distinct faunal assemblages were founds a "coastal" assemblage 2 to 28 km offshore and an "offshore" assemblage 37 to 111 km from shore. The coastal group was dominated by Osmeridae, Parophrys vetulus, Isopsetta isolepis, and Microgadus proximus. The offshore group was dominated by Sebastes spp., Stenobrachius leucopsarus, Tarletonbeania crenularis, Lyopsetta exilis, and Engraulis mordax. Peak abundance in both assemblages occurred between February and July when >90% of all larvae were taken. Larval distribution patterns in each assemblage were similar in 1971 and 1972, but larval abundance was greater in 1971 than 1972. Ninety-nine percent of the larvae in 53 taxa designated as coastal and 96% of the larvae in 31 taxa designated as offshore were taken 2 to 28km or 37 to 111 km offshore respectively. This separation of coastal and offshore larvae may be explained, in part, by adult spawning locations and current circulation patterns. The species of larvae present in the coastal assemblage were similar to those in Yaquina Bay, but dominant species were quite different. The coastal zone is an important spawning area for P. vetulus, which utilizes Yaquina Bay estuary as a nursery during part of its early life. Master files scanned at 600 ppi (256 Grayscale) using Capture Perfect 3.0.82 on a Canon DR-9080C in TIF format. PDF derivative scanned at 300 ppi (256 B&W, 256 Grayscale), using Capture Perfect 3.0.82, on a Canon DR-9080C. CVista PdfCompressor 4.0 was used for pdf compression and textual OCR.
"Data collected from an annual groundfish survey of the eastern Bering Sea shelf from 1975 to 2002 were used to estimate biomass and biodiversity indexes for two fish guilds: flatfish and roundfish. Biomass estimates indicated that several species of flatfish (particularly rock sole, arrowtooth flounder, and flathead sole), several large sculpins (Myoxocephalus spp.), bigmouth (Hemitripterus bolini), and skates (Bathyraja spp.) had increased. Declining species included several flatfish species and many smaller roundfish species of sculpins, eelpouts (Lycodes spp.), and sablefish (Anoplopoma fimbria). Biodiversity indexes were calculated by using biomass estimates for both guilds from 1975 through 2002 within three physical domains on the eastern Bering Sea shelf. Biodiversity trends were found to be generally declining within the roundfish guild and generally increasing within the flatfish guild and varied between inner, middle, and outer shelf domains. The trends in biodiversity indexes from this study correlated strongly with the regime shift reported for the late 1970s and 1980s."
"Juvenile chinook salmon,Oncorhynchus tshawytscha, from natal streams in California’s Central Valley demonstrated little estuarine dependency but grew rapidly once in coastal waters. We collected juvenile chinook salmon at locations spanning the San Francisco Estuary from the western side of the freshwater delta—at the confluence of the Sacramento and San Joaquin Rivers—to the estuary exit at the Golden Gate and in the coastal waters of the Gulf of the Farallones. Juveniles spent about 40 d migrating through the estuary at an estimated rate of 1.6 km/d or faster during their migration season (May and June 1997) toward the ocean. Mean growth in length (0.18 mm/d) and weight (0.02 g/d) was insignificant in young chinook salmon while in the estuary, but estimated daily growth of 0.6 mm/d and 0.5 g/d in the ocean was rapid (P≤0.001). Condition (K factor) declined in the estuary, but improved markedly in ocean fish. Total body protein, total lipid, triacylglycerols (TAG), polar lipids, cholesterol, and nonesterified fatty acids concentrations did not change in juveniles in the estuary, but total lipid and TAG were depleted in ocean juveniles. As young chinook migrated from freshwater to the ocean, their prey changed progressively in importance from invertebrates to fish larvae. Once in coastal waters, juvenile salmon appear to employ a strategy of rapid growth at the expense of energy reserves to increase survival potential. In 1997, environmental conditions did not impede development: freshwater discharge was above aver age and water temperatures were only slightly elevated, within the species’ tolerance. Data suggest that chinook salmon from California’s Central Valley have evolved a strong ecological propensity for a ocean-type life history. But unlike populations in the Pacific Northwest, they show little estuarine dependency and proceed to the ocean to benefit from the upwelling-driven, biologically productive coastal waters."
Commercial longline fishing data were analyzed and experiments were conducted with gear equipped with hook timers and time-depth recorders in the Reunion Island fishery (21 degrees 5'S lat., 53 degrees 28'E long.) to elucidate direct and indirect effects of the lunar cycle and other operational factors that affect catch rates, catch composition, fish behavior, capture time, and fish survival. Logbook data from 1998 through 2000, comprising 2009 sets, indicated that swordfish (Xiphias gladius) catch-per unit of effort (CPUE) increased during the first and last quarter of the lunar phase, whereas albacore (Thunnus alalunga) CPUE was highest during the full moon. Swordfish were caught rapidly after the longline was set and, like bigeye tuna (Thunnus obesus), they were caught during days characterized by a weak lunar illumination-mainly during low tide. We found a significant but very low influence of chemical lightsticks on CPUE and catch composition. At the time the longline was retrieved, six of the 11 species in the study had >40% survival. Hook timers indicated that only 8.4% of the swordfish were alive after 8 hours of capture, and two shark species (blue shark [Prionace glauca] and oceanic whitetip shark [Carcharhinus longimanus]) showed a greater resilience to capture: 29.3% and 23.5% were alive after 8 hours, respectively. Our results have implications for current fishing practices and we comment on the possibilities of modifying fishing strategies in order to reduce operational costs, bycatch, loss of target fish at sea, and detrimental impacts on the environment.
Reprinted from Fishery bulletin, Vol. 75 (1), pages 173-183. Dover and rex sole larvae attain an exceptionally large size and have a long pelagic life. Dover sole larvae (9-65 mm standard length) were collected in mid-water trawls and plankton nets during all months of the year. Judging from growth of larvae and occurrence in bottom trawls of recently metamorphosed juveniles, Dover sole are pelagic during their first year of life. Large larvae (50-65 mm standard length) are probably pelagic for over a year and few apparently are recruited to benthic populations. Dover sole larvae were most common in oceanic waters beyond the continental slope and in the upper 50 m of the water column. The rex sole larvae captured were 5-89 mm long. Average size and stage of development of larvae increased from March through February, and juveniles were common on the bottom during winter on the outer shelf. Thus the pelagic phase usually lasts about a year. Both rex and Dover sole may utilize the outer continental shelf-upper slope region for a nursery during early benthic life. Petrale sole larvae (10-22 mm standard length) were rare. They were collected only from March to June and appear to have a pelagic life of about 6 mo. Age-group 0 juveniles, uncommon in bottom trawl collections, were only captured on the inner continental shelf in the fall. Master files scanned at 600 ppi (256 Grayscale) using Capture Perfect 3.0.82 on a Canon DR-9080C in TIF format. PDF derivative scanned at 300 ppi (256 B&W), using Capture Perfect 3.0.82, on a Canon DR-9080C. CVista PdfCompressor 4.0 was used for pdf compression and textual OCR.
Species-specific restriction site variation in the 12S/16S rRNA and ND-3/ND-4 mtDNA regions was used to distinguish among 15 rockfish species of the genus Sebastes common to the waters of Alaska. Intraspecific variation exhibited by eight of the species (based on five individuals of each species) did not obscure the interspecific variation, except possibly between S. zacentrus and S. variegatus. Intraspecific nucleotide diversity averaged 0.0024 substitutions per nucleotide, whereas interspecific nucleotide divergence averaged 0.0249. In contrast, the average nucleotide divergences between Sebastes and two other scorpaenid species, Helicolenus hilgendorfi and Sebastolobus alascanus, were 0.0805 and 0.1073, respectively. Cladistic and phenetic analyses supported some, but not all, of the subgenera assignments of Sebastes. A scheme for distinguishing among the species studied was presented. Restriction sites of 10 restriction endonucleases were mapped in the two PCR-amplified mtDNA regions by using double digests. In all, we detected 153 sites corresponding to 640 (13.5%) of the 4815 nucleotides in the two regions combined. The ND-3/ND-4 region exhibited substantially more intraspecific, interspecific, and intergeneric variation than the 12S/16S rRNA region.
The wreckfish (Polyprion americanus), a commercially important, long-lived, demersal fish, is found in the eastern Atlantic from Norway to South Africa and in the western Atlantic from the Grand Banks, Newfoundland, to Argentina. Using bomb radiocarbon analysis, we validated the annual increment formation observed in otoliths and determined that increment counts are a good proxy for age. The maximum observed age was 80 years, more than double the previously reported maximum age of 39 years in the North Atlantic population. The updated fit of the length-at-age information to the von Bertalanffy growth model resulted in L∞, k, and t0 estimates of 1026 mm in fork length, 0.124/year, and −4.96 years, respectively. We used these updated values for maximum age and growth parameters to estimate rates of instantaneous and age-varying natural mortality, and found that instantaneous natural mortality ranged from 0.088 to 0.091 and age-varying natural mortality reached an asymptote of 0.07-0.12 by 15 years of age. This study highlights the need for age validation in long-lived fish species to prevent inaccurate estimates of age that ultimately can lead to mismanagement of a species.
Reproductive data from 95 mature female shortfin mako sharks, Isurus oxyrinchus Rafinesque, 1810, including 35 pregnant females, together with data on 450 postnatal fish were collected from around the world. Size at birth was approximately 70 cm total length (TL) and litter size varied from 4 to 25. increasing with maternal size. Embryo length-at-capture data predicted a gestation period of 15-18 months and late winter to midspring parturition in both hemispheres. A temporal analysis of uterus width index and gonadosomatic index of pregnant and postpartum females indicated that the reproductive cycle is three years. The median TL-at-maturity of females from the western North Atlantic (2.98 m) was greater than that of females from the Southern Hemisphere (2.73 m) and they were 16-19% heavier in the TL range of 2.5-3.5 m. Recently ovulated females and a litter with 2.6-3.3 cm TL embryos having external gills, a large yolk sac, and still inside their egg cases, are described. We describe a litter of embryos (52.0 cm TL) with huge yolk-filled stomachs. Litters of 59.9- and 68.8-cm-TL embryos showed a decline in the mass of the yolk-filled stomach from 29.1% to 10.9% of total mass and an increase in hepatosomatic indices from 3.7% to 7.0% as gestation advances. When the mass of the yolk-filled stomach was excluded, the mass-length relationship of shortfin mako embryos could be fitted with a power regression similar to that for postnatal fish. The condition factor of lamnid embryos (including yolk-stomach mass) reaches a maximum between 20 and 35 kg/m(3) when the embryos are midterm and have the largest yolk stomachs. The condition factor of alopiid embryos remains constant, indicating that no large yolk-filled stomach develops.
The dusky rockfish (Sebastes ciliatus) of the North Pacific Ocean has been considered a single variable species with light and dark forms distributed in deep and shallow water, respectively. These forms have been subjected to two distinct fisheries separately managed by federal and state agencies: the light deep form is captured in the offshore trawl fishery; the dark shallow form, in the nearshore jig fishery. The forms have been commonly recognized as the light dusky and dark dusky rockfishes. From morphological evidence correlated with color differences in some 400 specimens, we recognize two species corresponding with these color forms. Sebastes ciliatus (Tilesius) is the dark shallow-water species found in depths of 5-160 m in the western Aleutian Islands and eastern Bering Sea to British Columbia. The name Sebastes variabilis (Pallas) is resurrected from the synonymy of S. ciliatus to apply to the deeper water species known from depths of 12-675 m and ranging from Hokkaido, Japan, through the Aleutian Islands and eastern Bering Sea, to Oregon. Sebastes ciliatus is uniformly dark blue to black, gradually lightening on the ventrum, with a jet black peritoneum, a smaller symphyseal knob, and fewer lateral-line pores compared to S. variabilis. Sebastes variabilis is more variable in body color, ranging from light yellow to a more usual tan or greenish brown to a nearly uniform dark dorsum, but it invariably has a distinct red to white ventrum. Synonymies, diagnoses, descriptions, and geographic distributions are provided for each species.
The effect of maturation on relative growth of somatic tissues was investigated by measuring and comparing monthly changes in dry weight of somatic tissues and reproductive organs. In both sexes, reproductive tissues grew in relation to total body mass; at maturity female reproductive tissue was 16% of total dry body mass, whereas male reproductive tissue was 2.6%. In females, the relative mass of the mantle and head decreased during maturation, whereas the relative mass of the viscera increased. In males, the mass of the viscera increased with maturation, but no decreases occurred. The percentage composition of protein in the mantle and head of females for each maturity stage did not differ significantly. Far bath sexes, the digestive gland mass remained relatively constant throughout the different maturity stages and seasons, and analysis of stomach fullness indicated that feeding increased in the final maturity stages. All observations support the hypothesis that energy and nutrients for maturation are supplied mainly by diet rather than by stored resources,but that during maturation there is a shift of emphasis from somatic growth to gonadal development and vitellogenesis. Sepia pharaonis, which appears to be an intermittent multiple spawner, does not use protein from muscle tissue for developing and growing its reproduction tissues.
The life history of the Atlantic sharpnose shark (Rhizoprionodon terraenovae) was described from 1093 specimens collected from Virginia to northern Florida between April 1997 and March 1999. Longitudinally sectioned vertebral centra were used to age each specimen, and the periodicity of circuli deposition was verified through marginal increment analysis and focus-to-increment frequency distributions. Rhizoprionodon terraenovae reached a maximum size of 828 mm precaudal length (PCL) and a maximum age of 11+ years. Mean back-calculated lengths-at-age ranged from 445 mm PCL at age one to 785 mm PCL at age ten for females, and 448 mm PCL at age one to 747 mm PCL at age nine for males. Observed length-at-age data (estimated to 0.1 year) yielded the following von Bertalanffy parameters estimates: L∞= 749 mm PCL (SE=4.60), K = 0.49 (SE=0.020), and t0=-0.94 (SE=0.046) for females; and L∞=745 mm PCL (SE=5.93), K=0.50 (SE=0.024), and t0=-0.91 (SE= 0.052) for males. Sexual maturity was reached at age three and 611 mm PCL for females, and age three and 615 mm PCL for males. Rhizoprionodon terraenovae reproduced annually and had a gestation period of approximately 11 months. Litter size ranged from one to eight (mean=3.85) embyros, and increased with female PCL.
Northern rock sole (Lepidopsetta polyxystra Orr and Matarese, 2000) and southern rock sole (L. bilineata Ayres, 1855) from the Gulf of Alaska and northern rock sole from the Aleutian Islands were examined for gill parasites. Four species of copepod parasites were identified: Naobranchia occidentalis and Nectobrachia indivisa were the most common. Both parasites were more prevalent on northern rock sole (22% and 15%, respectively) than on southern rock sole (5% and 1%, respectively) in the Gulf of Alaska samples. Northern rock sole tended to have a greater mean intensity of Naobranchia occidentalis than southern rock sole but there was not a significant difference because of the high variance about the means; too few southern rock sole were infested by Nectobrachia indivisa for comparison. Northern rock sole from the Aleutian Islands region had a significantly greater prevalence (36%) and mean intensity (10.2/infested fish) of Naobranchia occidentalis than northern rock sole from the Gulf of Alaska (22%, and 4.4, respectively) but did not differ significantly in prevalence and mean intensity of Nectobrachia indivisa. Parasitized male northern rock sole from the Gulf of Alaska had a significantly reduced weight at length, indicating a possible effect of parasitism. Naobranchia occidentalis selectively infested larger northern rock sole and only the largest southern rock sole. Nectobrachia indivisa also were found on larger northern rock sole but did not infest enough southern rock sole to describe a trend. Southern rock sole males were not infested by either parasite. Naobranchia occidentalis preferred to infest the middle gill arches of hosts and Nectobrachia indivisa preferred to infest the exterior gill arches of hosts.
The whitetip flyingfish, Cheilopogon xenopterus, is an epipelagic resident of tropical and subtropical eastern Pacific waters. Its eggs are spherical, average 1.8 mm in diameter, and have an homogeneous yolk and no oil globule. About 53 filaments averaging 1 mm in length are evenly distributed on the chorion. The notochord flexes, fin-ray formation is nearly complete, and the characteristic larval pigmentation pattern is established prior to hatching at a larval length of about 2.8-3.3 mm. Larvae hatch with pigmented eyes, functional mouth, and little remaining yolk. Pectoral- and pelvic-fin rays initially are short but elongate rapidly to ca. 25-50% and 20-40% of body length, respectively. A pair of mandibular barbels form at about 4 mm and fuse mesially at about 8 mm. Scales begin to form along the lateral line at about 13-14 mm and cover the body by 26 mm. The characteristic pigment pattern, visible through the early juvenile stage, consists of the following: melanophores scattered over the mid- and hindbrain, continuing posteriorly as two rows (increasing to four or more rows) along the dorsal margin; a row of melanophores on the horizontal septum of the tail (after hatching); a patch on each side over the hypural area; and two rows along the anal-fin base. Internal pigment is present on the mid- and hindbrain, over the gut, and over the notochord. The pectoral and pelvic fins are sparsely pigmented at hatching and become increasingly pigmented with growth. A barred pigment pattern begins to develop on the body at about 8 mm and by the juvenile stage about six bars are present.
The number of adults and juveniles onshore declined 52% from 140 000 animals in 1956-60 to 68 000 in 1985, an annual rate of decline of at least 2.7%. Numbers have declined throughout the region, with the greatest declines in the E Aleutian Islands (79%), the least in the C Aleutian Islands (8%). Beginning in the late 1970s declines occurred in all areas, possibly associated with disease, prey availability or quality, or a combined effect of these and other factors. Factors which may contribute to the declines include the pre-1973 commercial harvests, entanglement of juveniles in marine debris, incidental takes in fisheries, and killing by fishermen. -from Authors
Apects of the life history of red porgy from the South Atlantic Bight (SAB) were examined for four periods (1972-74, 1979-81, 1988-90, and 1991-94), and annual changes in the age and growth of red porgy were described for data collected during 1988-94. The life history of red porgy during 1972-74 was assumed to represent that of an unfished population, although this population had been subject to light fishing pressure. From 1972-74 to 1979-81, the back-calculated size-at-age increased slightly for ages 2-8. By 1988-90 and 1991-94, however, the back-calculated size-at-age for the same age classes was significantly smaller than that in 1979-81. In addition, size-at-maturity and size-at-sexual-transition occurred at progressively smaller sizes for 1988-90 and 1991-94. The mean size-at-age (observed and back-calculated) declined for most ages between 1988 and 1994. Von Bertalanffy growth curves fitted to the mean back-calculated size-at-age for each year showed similar decreasing trends. Changes in life history may be a response to sustained 20-year overexploitation that has selectively removed individuals predisposed towards rapid growth and larger size.
Gag, Mycteroperca microlepis, is a large, slow-growing, protogynous grouper that probably makes annual migrations to specific locations to aggregate for spawning. During 1976-82, male gag constituted 19.6% of the sexually mature individuals taken during fishery-dependent and fishery-independent sampling along the southeast coast of the United States. A similar percentage of males was found in the Gulf of Mexico from 1977 to 1980; however, males made up only 1.9% of the population in the Gulf of Mexico during 1992. To assess the current sex ratio of gag along the southeast U.S. coast, an emergency rule was enacted by the Department of Commerce in January 1995 that required commercial vessels from North Carolina to southeast Florida to land gag with gonads intact. Histological examination of 2613 gonads of sexually mature gag collected from 18 January through 18 April 1995 revealed that 5.5% of the gag from the southeast Atlantic were male. There was a weak trend indicating that females reached maturity at a smaller size in 1994-95 than in 1976-82. Very few transitional specimens were collected during the spawning season. Most transitional individuals (79%) were taken during April through June immediately after the 1995 spawning season. Gag in spawning condition were landed during December through mid-May by fishermen working offshore from North Carolina to southeast Florida. In addition, gag in spawning condition were taken during research cruises documenting the occurrence of spawning north of Florida (off South Carolina and Georgia at depths ranging from 49 to 91 m).
A total of 12,180 king mackerel, Scomberomorus cavalla, collected from 1986 to 1992 from North Carolina to Yucatan, Mexico, and 2,033 collected in 1977 and 1978 from North Carolina to Texas were aged with whole or sectioned sagittal otoliths. Date were analyzed by region Atlantic Ocean, eastern Gulf of Mexico, and western Gulf-reflecting the currently recognized stocks. Maximum sizes of females aged were 152, 158, and 147 cm FL in the Atlantic, eastern Gulf, and western Gulf, whereas the largest males were 121,127, and 117 cm FL in those same regions. Maximum ages from the 1986-92 fish were 26, 21, and 24 yr for females and 24, 22, and 23 yr for males in the Atlantic, eastern Gulf, and western Gulf, respectively. Females grew faster and larger than males at every age in each region. A very consistent pattern of greatest growth in the eastern Gulf, intermediate in the western Gulf, and least in the Atlantic was present each year during 1986-92, most noticeably among females. During 1977-78, Atlantic females also had distinctly lower growth than Gulf fish. These consistent regional differences support the current hypothesis that there are three stocks as suggested by previous analyses of other types of data. Within a region and sex, growth was lower in 1977-78 than in 1986-92 in both the Atlantic and eastern Gulf, but higher for western Gulf females.
Estimates are derived from simple random sampling and stratified (by rookery size) random sampling using standard ("blow up') estimation procedure, and ratio and regression estimates (based on the same sampling procedure but taking advantage of a strong relationship between numbers of breeding males and live pups on the various rookeries). Evaluation of the sampling schemes and estimation methods is based on the performance of the estimators for 3 years (1965, 1970, 1975) of data for which the mark-recapture estimates from all 14 rookeries were available. Ratio estimates are preferred to estimates obtained from the standard procedure for both simple random sampling and stratified random sampling. Estimates from sampling plans based on 3 strata proved most satisfactory. The number of northern fur seal pups born on St. Paul Island decreased at approximately 7.5% per year during 1975-81. There was no statistically detectable trend in numbers born during 1981-86. -from Authors