Day and night abundance, distribution, and activity patterns of demersal fishes on Heceta Bank, Oregon

Most shallow-dwelling tropical marine fishes exhibit different activity patterns during the day and night but show similar transition behavior among habitat sites despite the dissimilar assemblages of the species. However, changes in species abundance, distribution, and activity patterns have only rarely been examined in temperate deepwater habitats during the day and night, where day-to-night differences in light intensity are extremely slight. Direct-observation surveys were conducted over several depths and habitat types on Heceta Bank, the largest rocky bank off the Oregon coast. Day and night fish community composition, relative density, and activity levels were compared by using videotape footage from a remotely operated vehicle (ROV) operated along paired transects. Habitat-specific abundance and activity were determined for 31 taxa or groups. General patterns observed were similar to shallow temperate day and night studies, with an overall increase in the abundance and activity of fishes during the day than at night, particularly in shallower cobble, boulder, and rock ridge habitats. Smaller schooling rockfishes (Sebastes spp.) were more abundant and active in day than in night transects, and sharpchin (S. zacentrus) and harlequin (S. variegatus) rockfish were significantly more abundant in night transects. Most taxa, however, did not exhibit distinct diurnal or nocturnal activity patterns. Rosethorn rockfish (S. helvomaculatus) and hagfishes (Eptatretus spp.) showed the clearest diurnal and nocturnal activity patterns, respectively. Because day and night distributions and activity patterns in demersal fishes are likely to influence both catchability and observability in bottom trawl and direct-count in situ surveys, the patterns observed in the current study should be considered for survey design and interpretation.

The Status of the United States Population of Night Shark, Carcharhinus signatus

Night sharks, Carcharhinus signatus, are an oceanic species generally occurring in outer continental shelf waters in the western North Atlantic Ocean including the Caribbean Sea and Gulf of Mexico. Although not targeted, night sharks make up a segment of the shark bycatch in the pelagic longline fishery. Historically, night sharks comprised a significant proportion of the artisanal Cuban shark fishery but today they are rarely caught. Although information from some fisheries has shown a decline in catches of night sharks, it is unclear whether this decline is due to changes in fishing tactics, market, or species identification. Despite the uncertainty in the decline, the night shark is currently listed as a species of concern due to alleged declines in abundance resulting from fishing effort, i.e. overutilization. To assess their relevance to the species of concern list, we collated available information on the night shark to provide an analysis of its status. Night shark landings were likely both over- and under-reported and thus probably did not reflect all commercial and recreational catches, and overall they have limited relevance to the current status of the species. Average size information has not changed considerably since the 1980’s based on information from the pelagic longline fishery when corrected for gear bias. Analysis of biological information indicates night sharks have intrinsic rates of increase (r) about 10% yr–1 and have moderate rebound potential and an intermediate generation time compared to other sharks. An analysis of trends in relative abundance from four data sources gave conflicting results, with one series in decline, two series increasing, and one series relatively flat. Based on the analysis of all currently available information, we believe the night shark does not qualify as a species of concern but should be retained on the prohibited species list as a precautionary approach to management until a more comprehensive stock assessment can be conducted.

Differences in Dolphin Mortality Rates in Night and Day Sets for the U.S. Eastern Tropical Pacific Tuna Purse Seine Fishery

Because dolphins sometimes travel with yellowfin tuna, Thunnus albacares, in the eastern tropical Pacific (ETP), purse seiners use the dolphins to locate and capture tuna schools. During the process of setting the purse seine nets, dolphins often become entangled and drown before they can be released. Data for the U.S. purse seine fleet in the ETP during 1979-88 show that dolphin mortality rates in sets made during the night are higher than mortality rates in sets made during the day. Even with efforts to reduce nightset mortality rates through the use of high intensity floodlights, night set mortality rates remain higher. The data are also used to simulate a regulation on the fishery aimed at eliminating night sets and show that dolphin mortality rates would decrease.

Age determination and growth of the night shark (Carcharhinus signatus) off the northeastern Brazilian coast

Age and growth of the night shark (Carcharhinus signatus) from areas off northeastern Brazil were determined from 317 unstained vertebral sections of 182 males (113–215 cm total length [TL]), 132 females (111.5–234.9 cm) and three individuals of unknown sex (169–242 cm). Although marginal increment (MI) analysis suggests that band formation occurs in the third and fourth trimesters in juveniles, it was inconclusive for adults. Thus, it was assumed that one band is formed annually. Births that occur over a protracted period may be the most important source of bias in MI analysis. An estimated average percent error of 2.4% was found in readings for individuals between two and seventeen years. The von Bertalanffy growth function (VBGF) showed no significant differences between sexes, and the model derived from back-calculated mean length at age best represented growth for the species (L∞=270 cm, K=0.11/yr, t0=–2.71 yr) when compared to the observed mean lengths at age and the Fabens’ method. Length-frequency analysis on 1055 specimens (93–260 cm) was used to verify age determination. Back-calculated size at birth was 66.8 cm and maturity was reached at 180–190 cm (age 8) for males and 200–205 cm (age ten) for females. Age composition, estimated from an age-length key, indicated that juveniles predominate in commercial catches, representing 74.3% of the catch. A growth rate of 25.4 cm/yr was estimated from birth to the first band (i.e. juveniles grow 38% of their birth length during the first year), and a growth rate of 8.55 cm/yr was estimated for eight- to ten-year-old adults.

Does the California market squid (Loligo opalescens) spawn naturally during the day or at night? A note on the successful use of ROVs to obtain basic fisheries biology data

The California market squid (Loligo opalescens Berry), also known as the opalescent inshore squid (FAO), plays a central role in the nearshore ecological communities of the west coast of the United States (Morejohn et al., 1978; Hixon, 1983) and it is also a prime focus of California fisheries, ranking first in dollar value and tons landed in recent years (Vojkovich, 1998). The life span of this species is only 7−10 months after hatching, as ascertained by aging statoliths (Butler et al., 1999; Jackson, 1994; Jackson and Domier, 2003) and mariculture trials (Yang, et al., 1986). Thus, annual recruitment is required to sustain the population. The spawning season ranges from April to November and spawning peaks from May to June. In some years there can be a smaller second peak in November. In Monterey Bay, the squids are fished directly on the egg beds, and the consequences of this practice for conservation and fisheries management are unknown but of some concern (Hanlon, 1998). Beginning in April 2000, we began a study of the in situ spawning behavior of L. opalescens in the southern Monterey Bay fishing area.

California Cooperative Fisheries Investigations. Hydrographic data report. Monterey Bay. July to December, 1974

In July 1974 Moss Landing Marine Laboratories began the continuation of the bi-weekly hydrographic observations in Monterey Bay. From 1951 to this date, these stations were sampled by personnel at Hopkins Marine Station in Pacific Grove. Small changes were made in the sampling routine: 1) to facilitate squid (Loligo opa1escens) studies, our observations were made at night, and 2) stations 1125 and 1154 are sampled in addition to five stations originally used by Hopkins Marine Station (2201, 2202, 2203, 2204, and 2205). These additional stations will provide important data of the nearshore environment. PDF contains 86 pages)

Effects of temperature on the biology of the northern shrimp, Pandalus borealis, in the Gulf of Maine

Length-frequency data collected from inshore and offshore locations in the Gulf of Maine in 1966-1968 indicated that ovigerous female northern shrimp (Pandalus borealis) first appeared offshore in August and September and migrated inshore in the fall and winter. Once eggs hatched, surviving females returned offshore. Juveniles and males migrated offshore during their first two years of life. Sex transition occurred in both inshore and oll'shore waters, but most males changed sex offshore during their third and fourth years. Most shrimp changed sex and matured as females for the first time in their fourth year. Smaller females and females exposed to colder bottom temperatures spawned first. The incidence of egg parasitism peaked in January and was higher for shrimp exposed to warmer bottom temperatures. Accelerated growth at higher temperatures appeared to result in earlier or more rapid sex transition. Males and non-ovigerous females were observed to make diurnal vertical migrations, but were not found in near- surface waters where the temperature exceeded 6°C. Ovigerous females fed more heavily on benthic molluscs in inshore waters in the winter, presumably because the egg masses they were carrying prevented them from migrating vertically at night. Northern shrimp were more abundant in the southwestern region of the Gulf of Maine where bottom temperatures remain low throughout the year. Bottom trawl catch rates were highest in Jeffreys Basin where bottom temperatures were lower than at any other sampling location. Catch rates throughout the study area were inversely related to bottom temperature and reached a maximum at 3°C. An increase of 40% in fecundity between 1973 and 1979 was associated with a decline of 2-3°C in April-July offshore bottom temperatures. Furthermore, a decrease in mean fecundity per 25 mm female between 1965 and 1970 was linearly related to reduced landings between 1969 and 1974. It is hypothesized that temperature-induced changes in fecundity and, possibly, in the extent of egg mortality due to parasitism, may provide a mechanism which could partially account for changes in the size of the Gulf of Maine northern shrimp population during the last thirty years. (PDF file contains 28 pages.)

A Comparison of the Range and Movements of Acmaea digitalis Eschscholtz, Acmaea scutum Eschscholtz, Acmaea limatula Carpenter and Lottia gigantea Sowerby

Ten limpets (4 Acmaea digitalis , 4 Acmaea scutum, 1 Acmaea limatula, and 1 Lottia gigantea) were marked and their movements observed over a thirteen day period. Recordings of positions were made on a map, and the path of each was drawn on the map from day to day. Acmaea digitalis showed the greatest range, mostly in a vertical direction, and moved usually at night during high tide. Acmaea scutum showed a more limited range in a horizontal direction, and moved both day and night during high tide. Acmaea limatula had a horizontal range similar to A. scutum,, but exhibited no movement during the day time. Lottia gigantea had the most restricted range of any limpet studied, and moved only at night during high tide. This is a student paper done for a University of California Berkeley Zoology class. Since UCB didn't have its own marine lab at the time, it rented space at Hopkins Marine Station where this work was done. Gene Haderlie went on to earn his Ph.D. from Berkeley and later became a Professor at the Naval Post Graduate School in Monterey. (PDF contains 23 pages)

Diel differences in catches of Western Baltic Spring Spawning Herring Larvae (Clupea harengus)

Comparative night and day catches of herring larvae were taken during the Rügen-Herring-Larval-Survey (RHLS) in 2007 and 2008 in the Greifswalder Bodden which is the main spawning area of the Western Baltic Spring Spawning Herring. The quantities and the size composition of larvae caught during night and day were examined. During night more larvae were caught compared to the samples taken at daytime, especially with larvae larger than 25 mm. This indicates avoidance reactions, which increase with the developmental stage of the larvae. The differences of the night and day catches are relatively constant until a length of about 25 mm, thus the night/day effect does not influence estimations concerning larvae smaller than 25 mm (e.g. N20 index). There might be an impact on estimations for larger larvae due to the night/day effect. For further research other aspects like cloud coverage at night, phase of the moon, underwater visibility and turbidity should be taken into account. These aspects might influence the avoidance reactions.

Einfluss des Tag-Nacht-Verhaltens von Fischen auf das Ergebnis hydroakustischer Messungen

Echo integration is an established method for stock estimation. However, this method is not free of errors like every other measuring method. Especially the variation between day and night behaviour of fish may lead to large measuring errors. A new method is represented detecting such systematic errors, exemplified by investigations during the international hydroacoustic survey on the spring spawning herring in the Norwegian Sea. For this method all measured sA-values are sorted by starting time of the measuring unit distance. In order to reduce random influences a moving average over five time intervals is computed. When displaying these values in a diagram makes it is very easy to detect systematic errors based on the differences in day-night behaviour. For both species, herring and blue whiting, stock estimations are calculated based on the measured sA-values and the results of the analysed trawl catches. The influence of the differnt day and night behaviour of herring on the results of its biomass estimation is rather low. For blue whiting the measured values were about three time higher during day time than during night time. The result of this investigation should initiate a change of the evaluation procedure for stock estimation based on hydroacoustic measurements.

Results of the first hydroacoustic survey of the Ugandan waters of Lake Victoria

A lakewide hydroacoustic research programme was designed in the Ugandan waters of Lake Victoria in order to ascertain the status of fish stocks. Data obtained from the hydroacoustic surveys were complemented with by catch data from multi mesh gillnets and frame trawls to validate acoustic estimates. Fish were distributed over the whole survey area, though the densities and species composition varied from place to place. Echo traces showed the fish formed schools during daytime and became more dispersed towards evening. Approximately equivalent indices of abundance were estimated for Rastrineobola argentea and Haplocromines. The distribution of the freshwater prawn, Caridina nilotica and the lakefly Chaoborus sp. was patchy. Dense swarms of Chaoborus larvae were observed to disperse from the lake bottom as the night approached thus assuring echo-traces formed by fish on the echogram and making their interpretation difficult. Caridina nilotica were observed to form dense echo-traces at the thermocline

Selection of efficient hanging ratios of gillnet on fish catch in Lake Kainji, as means of alleviating poverty among artisanal fishermen in Nigeria

Five experimental gillnet each measuring 50mx 3m nylon multi filament netting of 3" by210/2 mesh size were constructed using 40%, 45%, 50%, 55% and 60% hanging percentages, the report was carried out at Yunawa fishing village on the eastern bank of Lake Kainji. The nets were set over night (6 hours approximately). Between April-July 2004, the fish caught by the five nets were recorded taking into consideration the three mode of capture i.e. enmeshing entanglement and wedging Weight number and percentage mean weight and number based on species at five different hanging ratios were analyzed in general 50% hanging ratio was found to be the best followed by 40% among others. There was significant difference (P<0.05) in the mode of capture for both hanging ratios. Most of the fish were caught by entanglement i.e. about 83% of the catch was by entanglement while 505 hanging ratio was the best considered after the report. The occurrence of species of the five hanging ratios has significant difference (P<0.05) in terms of catch by weight and number

Analyse des Fluchtverhaltens von Fischen auf Schiffsgeräusche mit hydroakustischen Methoden

Investigations on the avoidance reactions of pelagic schooling fish (herring and sprat) released by an approaching fishery vessel were carried out during the 378th cruise of FRC "Solea" from 25 September to 3 October 1995 in the Arkona Sea, southern Baltic. An echosounder system EK 500/BI500 with a 38 kHz transducer mounted on a towed body as weIl as a 120 kHz hull mounted transducer were used. Fish densities were measured synchronously as well as under the ship as at a laterally distances from the ship by the transducer of the towed body. By these means the variation of fish densities up to a certain distance from the ship is possible. The advantage of using an echo integrating system for these measurements is, that it works also for not schooling fish and under conditions where schooling fish disperse (e.g. at night).

The avifauna of Laguna Llancanelo (Mendoza, Argentina), a South American wetland of international importance

Laguna Llancanelo is a large (40,000 ha), very shallow (less than 3 m deep), inland saline waterbody, located in southern Mendoza, Argentina. A survey of the avifauna was undertaken during 1983 to 1985; field trips were made mostly to the northeastern and central-western sectors of the lagoon, in the months of April, May, September, October and December. Complementary studies were made by an aerial survey and assessments of terrestrial birds in the surroundings of the lagoon. A total of 64 species in 22 families of birds usually associated with aquatic environments were recorded. The best-represented families of aquatic birds in terms of numbers of species were: Anatidae (13 swans, geese, ducks), Scolopacidae (7 sandpipers and other small waders), Ardeidae (6 herons, bitterns, egrets, Podicipedidae (4 grebes), Rallidae (4 rails, coots) and Charadriidae (4 plovers, lapwings). The most abundant nesting birds on the lagoon were: Black-necked swan Cygnus melancoryphus (824), silvery grebe Podiceps occipitalis (202) and black-crowned night heron Nycticorax nycticorax (100).

Investigations on the vertical migration of planktonic Crustacea in the Bodensee-Obersee. [Translation from: Schriften des Vereins fur Geschichte des Bodensees und seiner Umgebung, 87, 177-187, 1969.]

The vertical zoning of the planktonic Crustacea in a lake is the expression of a complex set of different factors. Besides the measurable, external influences such as light, temperature, acid and C02 stratification, a particularly large part is played by internal factors, which co-ordinate a specific reaction in each species depending on state of development, age and sex. Supporting this extensive, predictable, annual course of diurnal depths and the daily vertical migrations, whose extent is again dependent on external conditions, primarily of course on the amount of light. The individual factors mentioned, however, are here also of great significance. Within the scope of a long-term study of the planktonic Copepoda of Lake Constance, some day and night series were in 1963 also carried out in the Obersee, in order to obtain at least volumetric data on the extent of the daily migrations of these creatures.