Analyzing and mapping fish assemblages off central California, USA

This study describes fish assemblages and their spatial patterns off the coast of California from Point Arena to Point Sal, by combining the results of the multivariate analyses of several fisheries datasets with a geographic information system. In order to provide comprehensive spatial coverage for the areas of inshore, continental shelf, and continental slope, three fisheries datasets were analyzed: 1) Inshore: the California Department of Fish and Game dataset of fishery-dependent commercial passenger fishing vessel trips that targeted rockfish; 2) Continental Shelf: the National Marine Fisheries Service (NMFS) fishery-independent bottom trawls; and 3) Continental Slope: the NMFS fishery-independent bottom trawls on the continental slope. One-hundred seven species were analyzed. These species represented those captured in at least 5% of the fishing trips or trawls in at least one of the three data sets. We analyzed each of the three datasets separately, and the three sets of results were combined to define 28 species assemblages and 23 site groups. A species assemblage consisted of species caught together, whereas a site group consisted of fishing trips or trawl locations that tended to have the same species assemblages. At the scale of these datasets, 97% of all site groups were significantly segregated by depth.

Biogeographic characterization of fish communities and associated benthic habitats within the Flower Garden Banks National Marine Sanctuary: sampling design and implementation of scuba surveys on the coral caps

The Flower Garden Banks National Marine Sanctuary (FGBNMS) is located in the northwestern Gulf of Mexico approximately 180 km south of Galveston, Texas. The sanctuary’s distance from shore combined with its depth (the coral caps reach to within approximately 17 m of the surface) result in limited exposure of this coral reef ecosystem to natural and human-induced impacts compared to other coral reefs of the western Atlantic. In spite of this, the sanctuary still confronts serious impacts including hurricanes events, recent outbreaks of coral disease, an increase in the frequency of coral bleaching and the massive Diadema antillarum die-off during the mid-1980s. Anthropogenic impacts include large vessel anchoring, commercial and recreational fishing, recreational scuba diving, and oil and gas related activities. The FGBNMS was designated in 1992 to help protect against some of these impacts. Basic monitoring and research efforts have been conducted on the banks since the 1970s. Early on, these efforts focused primarily on describing the benthic communities (corals, sponges) and providing qualitative characterizations of the fish community. Subsequently, more quantitative work has been conducted; however, it has been limited in spatial scope. To complement these efforts, the current study addresses the following two goals put forth by sanctuary management: 1) to develop a sampling design for monitoring benthic fish communities across the coral caps; and 2) to obtain a spatial and quantitative characterization of those communities and their associated habitats.

Boat wakes and their influence on erosion in the Atlantic Intracoastal Waterway, North Carolina

Boat wakes in the Atlantic Intracoastal Waterway (AIWW) of North Carolina occur in environments not normally subjected to (wind) wave events, making sections of AIWW potentially vulnerable to extreme wave events generated by boat wakes. The Snow’s Cut area that links the Cape Fear River to the AIWW is an area identified by the Wilmington District of the U.S. Army Corps of Engineers as having significant erosion issues; it was hypothesized that this erosion could be being exacerbated by boat wakes. We compared the boat wakes for six combinations of boat length and speed with the top 5% wind events. We also computed the benthic shear stress associated with boat wakes and whether sediment would move (erode) under those conditions. Finally, we compared the transit time across Snow’s Cut for each speed. We focused on two size classes of V-hulled boats (7 and 16m) representative of AIWW traffic and on three boat speeds (3, 10 and 20 knots). We found that at 10 knots when the boat was plowing and not yet on plane, boat wake height and potential erosion was greatest. Wakes and forecast erosion were slightly mitigated at higher, planing speeds. Vessel speeds greater than 7 knots were forecast to generate wakes and sediment movement zones greatly exceeding that arising from natural wind events. We posit that vessels larger than 7m in length transiting Snow’s Cut (and likely many other fetch-restricted areas of the AIWW) frequently generate wakes of heights that result in sediment movement over large extents of the AIWW nearshore area, substantially in exceedance of natural wind wave events. If the speed, particularly of large V-hulled vessels (here represented by the 16m length class), were reduced to pre-plowing levels (~ 7 knots down from 20), transit times for Snow’s Cut would be increased approximately 10 minutes but based on our simulations would likely substantially reduce the creation of erosion-generating boat wakes. It is likely that boat wakes significantly exceed wind wave background for much of the AIWW and similar analyses may be useful in identifying management options.

Fish lost at sea: the effect of soak time on pelagic longline catches

Our analyses of observer records reveal that abundance estimates are strongly influenced by the timing of longline operations in relation to dawn and dusk and soak time— the amount of time that baited hooks are available in the water. Catch data will underestimate the total mortality of several species because hooked animals are “lost at sea.” They fall off, are removed, or escape from the hook before the longline is retrieved. For example, longline segments with soak times of 20 hours were retrieved with fewer skipjack tuna and seabirds than segments with soak times of 5 hours. The mortality of some seabird species is up to 45% higher than previously estimated. The effects of soak time and timing vary considerably between species. Soak time and exposure to dusk periods have strong positive effects on the catch rates of many species. In particular, the catch rates of most shark and billfish species increase with soak time. At the end of longline retrieval, for example, expected catch rates for broadbill swordfish are four times those at the beginning of retrieval. Survival of the animal while it is hooked on the longline appears to be an important factor determining whether it is eventually brought on board the vessel. Catch rates of species that survive being hooked (e.g. blue shark) increase with soak time. In contrast, skipjack tuna and seabirds are usually dead at the time of retrieval. Their catch rates decline with time, perhaps because scavengers can easily remove hooked animals that are dead. The results of our study have important implications for fishery management and assessments that rely on longline catch data. A reduction in soak time since longlining commenced in the 1950s has introduced a systematic bias in estimates of mortality levels and abundance. The abundance of species like seabirds has been over-estimated in recent years. Simple modifications to procedures for data collection, such as recording the number of hooks retrieved without baits, would greatly improve mortality estimates.

Small-boat surveys for coastal dolphins: line-transect surveys of Hector’s dolphins (Cephalorhynchus hectori)

Management of coastal species of small cetaceans is often impeded by a lack of robust estimates of their abundance. In the Austral summers of 1997−98, 1998−99, and 1999−2000 we conducted line-transect surveys of Hector’s dolphin (Cephalorhynchus hectori) abundance off the north, east, and south coasts of the South Island of New Zealand. Survey methods were modified for the use of a 15-m sailing catamaran, which was equipped with a collapsible sighting platform giving observers an eye-height of 6 m. Eighty-six percent of 2061 km of survey effort was allocated to inshore waters (4 nautical miles [nmi] or 7.4 km from shore), and the remainder to offshore waters (4−10 nmi or 7.4–18.5 km from shore). Transects were placed at 45° to the shore and spaced apart by 1, 2, 4, or 8 nmi according to pre-existing data on dolphin density. Survey effort within strata was uniform. Detection functions for sheltered waters and open coasts were fitted separately for each survey. The effect of attraction of dolphins to the survey vessel and the fraction of dolphins missed on the trackline were assessed with simultaneous boat and helicopter surveys in January 1999. Hector’s dolphin abundance in the coastal zone to 4 nmi offshore was calculated at 1880 individuals (CV=15.7%, log-normal 95% CI=1384−2554). These surveys are the first line-transect surveys for cetaceans in New Zealand’s coastal waters.

Distribution, demography, and discard mortality of crabs caught as bycatch in an experimental pot fishery for toothfish (Dissostichus eleginoides) in the South Atlantic

Between March 2000 and April 2001 two commercial fishing vessels fished for toothfish (Dissostichus eleginoides) off South Georgia using pots. A significant number of lithodid crabs (three species of Paralomis spp.) were caught as bycatch. Paralomis spinosissima occurred in shallow water, generally shallower than 700 m. Paralomis anamerae, not previously reported from this area and therefore representing a considerable southerly extension in the reported geographic range of this species, had an intermediate depth distribution from 400 to 800 m. Paralomis formosa was present in shallow waters but reached much higher catch levels (and, presumably, densities) between 800 and 1400 m. Differences were also noted in depth distribution of the sexes and size of crabs. Depth, soak time, and area were found to significantly influence crab catch rates. Few crabs (3% of P. spinosissima and 7% of P. formosa) were males above the legal size limit and could therefore be retained. All other crabs were discarded. Most crabs (>99% of P. formosa, >97% of P. spinosissima, and >90% of P. anamerae) were lively on arrival on deck and at subsequent discard. Mortality rates estimated from re-immersion experiments indicated that on the vessel where pots were emptied directly onto the factory conveyor belt 78–89% of crabs would survive discarding, whereas on the vessel where crabs were emptied down a vertical chute prior to being sorted, survivorship was 38–58%. Of the three, P. anamerae was the most vulnerable to handling onboard and sub-sequent discarding. Paralomis spinosissima seemed more vulnerable than P. formosa.

The physiological effects of multiple forced submergences in loggerhead sea turtles (Caretta caretta)

Sea turtles are subjected to involuntary submergence and potential mortality due to incidental capture by the commercial shrimp fishing industry. Despite implementation of turtle excluder devices (TEDs) to reduce at-sea mortality, dead stranded turtles continue to be found in near-record numbers along the coasts of the western Atlantic Ocean and northern Gulf of Mexico. Although this mortality may be due to an increase in the number of turtles available to strand, one alternative explanation is that sea turtles are repetitively submerged (as one fishing vessel follows the path of another) in legal TEDs. In the present study, laboratory and field investigations were undertaken to examine the physiological effects of multiple submergence of loggerhead sea turtles (Caretta caretta). Turtles in the laboratory study were confined during the submersion episodes, whereas under field conditions, turtles were released directly into TED-equipped commercial fishing nets. Under laboratory and field conditions, pre- and postsubmergence blood samples were collected from turtles submerged three times at 7.5 min per episode with an in-water rest interval of 10, 42, or 180 min between submergences. Analyses of pre- and postsubmergence blood samples revealed that the initial submergence produced a severe and pronounced metabolic and respiratory acidosis in all turtles. Successive submergences produced significant changes in blood pH, Pco2, and lactate, although the magnitude of the acid-base imbalance was substantially reduced as the number of submergences increased. In addition, increasing the interval between successive submergences permitted greater recovery of blood homeostasis. No turtles died during these studies. Taken together, these data suggest that repetitive sub-mergence of sea turtles in TEDs would not significantly affect their survival potential provided that the animal has an adequate rest interval at the surface between successive submergences.

Length-weight relationship of Upeneus sulphureus (Cuvier) collected off Maharashtra coast

The length-weight relationship of Upeneus sulphureus was studied on the basis of 125 females and 103 males, collected during the 27th cruise of research vessel M.V. Saraswati in the month of September, 1984. The correlation coefficient was found significant at 5% and 1% level respectively for male and female. In both the sexes, the regression co-efficient was found higher than three. Analysis of covariance was also carried out for the F test and F distribution.

Fish catch composition in relation to some hydrographic observations along the Bombay Ratnagiri coast

Hydrographic parameters in relation to fish catch composition within the depth range of 30 m to 97 m at 15 different stations off the Bombay to Ratnagiri coast were studied from onboard the vessel M.V. Saraswathi, a 36.5 meter deepsea going research-cum-training vessel during her 58th cruise from the 17th to the 27th December 1986. The study indicates the abundance of Trichiurus sp, Priacanthus sp and Arius sp. Fluctuations in the zooplankton biomass and faunistic composition in the area are examined in relation to some important hydrographic parameters.

Deepwater prawns and lobsters off the Kerala coast

Majority of the prawn catch of the Kerala coast comes from the inshore regions within the 10 fathom line. A bottom deposit formed of fine mud rich in humus is found to be the ideal condition for the penaeid prawns. Similarly the lobster is observed in large numbers at localised areas very near the coast in the crevices of rocks. Though it has been observed that prawns and lobsters exist in deep water as well under different conditions, our knowledge about these forms along the Indian coasts is very scanty, being restricted to the works of Spence Bate, Alcock, De Man and Ramadan. Recently, during the cruises of the University Research Vessel Conch off the Kerala Coast (1958-1963) two species of deep water prawns and one species of lobster were collected from depths 100 - 180 fathoms. Of these, Penaeopsis philippi is found in large numbers occupying an almost continuous bed extending from Anjengo to Mangalore, while P. rectacutus has a restricted appearance between Cochin and Calicut. However, some sort of year to year variation has also been observed regarding the abundance of the species at various stations. Peurulus sewelli has a more restricted distribution, the maximum number being found between Puvar and Cochin. Attempt has been made to correlate the occurrence of the species with the hydrological conditions at the bottom and the nature of the substratum. It is observed that Peurulus sewelli occupies a more or less hard bed formed of sand with shell fragments or stones and small percentage of silt, the bottom temperature at the stations varying from 11°C to l4°C. P. sewelli is a more or less permanent inhabitant of the edge of the continental shell off the Kerala Coast worthy of attention for detailed investigation with a view to explore the possibilities of commercial exploitation.

Prawn fishing by M.F.V. Jheenga in Bombay waters

The design and construction of the motor fishing vessel Jheenga of the Deep Sea Fishing Station of the Government of India, Bombay, the areas covered and the gear used by her in 1959-63 are described. The prawn catches in relation to the total catches, and their catch rates in different months in area 18-72 in Bombay region which was fished continuously during the five years period have been studied with a view to ascertaining their seasonal abundance. The results indicate the availability of the prawns in the region for the major part of the year from March to October-November. High catches with high catch rates forming high percentage of their abundance in total catches are obtained in July to October.

Standardisation and mass production of shrimp trawlers and other fishing boats in India

This paper deals with the existing fishing crafts, new vessel types, boat building programmes, their standardisation and mass-production in India.

Hydrographic winch

A winch suitable for lowering and hauling up of costly hydrographic apparatus like Bathy-thermograph, Reversible thermometers, Current flow meters etc., was designed, fabricated and tested at Off Shore Fishing Station, Cochin. The first model of this winch is in use on board the motor vessel Pratap, a Tuna Long linger.

Comparative fishing ability and economic efficiency of mechanised trawlers operating along the Kerala coast

This study was undertaken with a view to finding out the comparative fishing ability and economic performance of different fishing vessel sizes 9.15m (30'), 9.76m (32') and 10.97m (36') designed by the Central Institute of Fisheries Technology and operating along the Kerala coast. Data were collected from selected vessels of these sizes for four consecutive fishing seasons from 1964-65 to 1967-68. The catch/unit effort and total effort per year for the 10.97m (36') vessels were much better than those for the 9.76m (32') vessels. The yearly landings and the crew remuneration for the former were about twice those of the 9.76m (32') vessels. The economic efficiency of the 10.97m (36') vessels was also much better. The decline in landings per year in both size groups was more due to the reduction in the effort per year than the decline in catch/unit effort.

Histological distribution and ultrastructure of exocrine pancreas in Indian major carp (Labeo rohita Ham.) and its alteration in aflatoxicosis

The distribution pattern of exocrine pancreas in Labeo rohita besides its general location along the course of intestinal mesentery was studied. It is evenly distributed within the liver around portal vessels and also within the spleen near a blood vessel. On ultrastructure, two cell types of different degrees of staining intensities containing abundant rough endoplasmic reticulum, mitochondria, pre-zymogen and zymogen granules were marked. During aflatoxicosis, the mesenteric pancreas and hepatic pancreas were mostly affected revealing necrotic changes to acini. The zymogen granular activities were markedly reduced. Ultra structurally, the rough endoplasmic reticulum was fully dilated and formed whorled pattern. The damage to the exocrine pancreas might be affecting digestive enzymes' secretion which may be one of the causes of aflatoxin-induced anorexia in fish.