Grenadiers of the World Oceans: Biology, Stock Assessment, and Fisheries

<em>Abstract</em>.—The objective of this study is to describe the distribution patterns of abundance and biomass, on a geographic and bathymetric basis, of the main macrourid species of Mozambique waters. Catch data from a demersal trawl survey (<EM>MOZAMBIQUE 07</EM>) were analyzed. The survey covered the continental shelf and upper-middle slope from 17°00’S to 26°50’S and from 100–700 m depth. Fourteen macrourid species were collected from 200 m and deeper. The most abundant species and the highest in biomass were <em>Coelorinchus braueri</em>, <em>C. trunovi, C. denticulatus</em>, <em>Ventrifossa nasuta</em>, and <em>Malacocephalus laevis</em>. Only those five species were analyzed in detail. The occurrence and yields by geographic and bathymetric range of these main species seem to reveal the existence of some species-specific preference for determinate depth ranges and/or geographic areas. Preanal length-weight relationships were estimated for <em>C. braueri, C. trunovi, </em>and <em>V. nasuta</em>: <em>a</em>= 0.00071; 0.00020; 0.00080; <em>b</em>= 2.50; 2.80; 2.76 and <em>r</em>²= 0.93; 0.97; 0.78, respectively.

Grenadiers of the World Oceans: Biology, Stock Assessment, and Fisheries

<em>Abstract.</em>—The Chilean fishes of the family Macrouridae have historically been of little interest to the fisheries community in the SE Pacific. Landings of these fishes have only been officially recorded since 2000. Nevertheless there is evidence that macrourids have been incidentally caught as by-catch since the middle of the 20^th century. Species of the genera <em>Coelorinchus </em>(formerly known as <em>Caelorinchus</em>), <em>Coryphaenoides</em>, <em>Lucigadus</em>, <em>Macrourus </em>and <em>Nezumia </em>are common as by-catch. It now appears important to apply fisheries management to these species, recording them as a unit, but obtaining objective data for each species. This should include an overall perspective on the species having a wide geographic distribution.

Grenadiers of the World Oceans: Biology, Stock Assessment, and Fisheries

<em>Abstract</em>.—An exploratory longline fishery for toothfish (<em>Dissostichus </em>spp.) in the Ross Sea, Antarctica has been carried out since 1997. The main bycatch species in this fishery is the grenadier, <em>Macrourus whitsoni. </em>No assessments have been carried out of the impact of the fishery on grenadiers, although they have life history characteristics that make them vulnerable to overexploitation. The aims of this research were two-fold; firstly, to characterize the bycatch fishery and to determine factors affecting bycatch rates; and secondly to examine potential methods of monitoring its abundance. A standardized CPUE analysis was used to determine factors affecting bycatch rates of grenadiers in the fishery. The analysis was based on fine-scale haul-by-haul data from all vessels in the fishery from 1999 to 2005. The major factors influencing grenadier bycatch were vessel, area, and depth. Catch rates of grenadiers were highest along the continental slope of the Ross Sea in depths from 600 to 1000 m, and there was an order of magnitude difference in grenadier catch rates between different vessels. Examination of vessel characteristics showed that catch rates of grenadiers were significantly lower with the Spanish line system than with the autoline system. There are several plausible reasons for this difference, including hook location with respect to the seabed, bait type, and differences in levels of reporting of bycatch between vessels. Various approaches to monitoring and assessing grenadiers in the Ross Sea fishery were explored. We conclude that the year effect from the standardized CPUE analysis is unlikely to be monitoring abundance but instead probably reflect changes in gear characteristics, fisher behavior, and targeting of effort. Trends in the length composition of the catch are confounded with depth, and are also of limited value at present. We consider that the best approach to obtaining abundance estimates for grenadiers in the Ross Sea would be to carry out a random bottom trawl survey of the continental slope.

Grenadiers of the World Oceans: Biology, Stock Assessment, and Fisheries

<em>Abstract</em>.—Total body length of roundnose grenadier <em>Coryphaenoides rupestris </em>reaches 123 cm at maximum observed age of 30 years. In the Northwest Atlantic, predominating length is 50–70 cm, in the area of Mid-Atlantic Ridge and off Europe, 50–90 cm. Average length at maturity is 76 cm. Main spawning takes place in the Northeast Atlantic in summer-autumn. Mean fecundity is 30,000 eggs. Grenadier occur mainly near the bottom, but somtimes in the pelagic layer. Vertical migrations are very variable. Long distance horizontal migrations of adults have not been recorded. There is no consensus about population structure. In the Northwest Atlantic the greatest catch (83,700 t) was taken in 1971. Since then the fishery declined until it was stopped completely. On the Mid-Atlantic Ridge, the maximum catch (29,900 t) was taken in 1973, after which catches decreased. In the last 15 years, in the European waters, catches increased and reached 28,900 t in 2004. In the majority of the areas the stock size is at the low level. In the Northeast Atlantic (including the Mid-Atlantic Ridge) the fishery is regulated by NEAFC by the restriction of fishing effort and closed areas. In the Northwest Atlantic, directed fishery is banned by NAFO. In the North Atlantic, in the whole fishing period, the international catch amounted to about 1,000,000 t.

Grenadiers of the World Oceans: Biology, Stock Assessment, and Fisheries

<em>Abstract</em>.—The biology and fisheries of macrourid species in the NE Atlantic are reviewed. Of about 30 species that occur within that area, the roundnose grenadier <em>Coryphaenoides rupestris </em>is one of the main target species of deep-water fisheries. Roughhead grenadier <em>Macrourus berglax </em>is a minor bycatch of other deep-water fisheries and an occasional target of some small fisheries. Other macrourid species are not commercially exploited because they are too small and/or in too deep waters, but some are also taken as accidental bycatch. There are three main fisheries for roundnose grenadier: north and west of the British Isles, Skagerrak, and Mid-Atlantic Ridge. The Skagerrak fishery is mainly for fish meal while the others are for human consumption. Due to data availability, a range of assessment methods has been trialled primarily for stocks to the north and west of the British Isles. Although uncertain, these assessments provide evidence that the stock has been severely depleted. Fisheries were largely unregulated until the early 2000s, but following repeated International Council for the Exploration of the Sea (ICES) advice, total allowable catches were introduced in 2003 together with effort and capacity regulations. Roundnose grenadier is the most studied species. It lives more than 50 years, compared to 30 years or more for roughhead grenadier. The limited knowledge of other species suggests a contrasting picture of maximum age ranging from 10 to 40 years. Taking into account the limited biological knowledge for these species, the pros and cons of the current management regime are discussed.

Grenadiers of the World Oceans: Biology, Stock Assessment, and Fisheries

<em>Abstract.</em>—Extensive trawling efforts off Taiwan, supplemented by collections from trawlers’ harvest at several local fishing harbors, have raised the total number of Taiwan’s grenadier fishes to 71 species in 18 genera and 3 families. Despite a relatively limited coastline (500 nautical miles), the species diversity in Taiwan is very high. The largest genus <em>Coelorinchus </em>(formerly known as <em>Caelorinchus</em>) is represented by 21 species, followed by <em>Ventrifossa </em>with 8, and <em>Nezumia </em>with 6. All other genera had five or fewer representatives. Five species were described based on specimens from Taiwan, and two of them, <em>Coelorinchus leptorhinus </em>and <em>C. sheni, </em>have not been reported elsewhere. A total of 33 species and 10 genera are newly recorded from Taiwan; these were collected only within the past two years. Because the maximum depth trawled only reached about 2,000 m in this study, it should be expected that more deeper-water grenadiers will be found in the future. Our depth-distribution data-set of collected specimens and depth ranges from 55 stations were insufficient to effectively separate the species into groups using multivariate statistical analysis. However, the factors influencing grenadier species composition in this study still can be recognized as per the following sequence: water depth, geographical region, and type of net. The vertical distribution of grenadiers in Taiwan appears to have a separation at 600 m and 1000 m. An annotated species checklist with ASIZP cataloged specimens documenting Taiwan distributions, and detailed collecting information, including body size, location, and depth range are provided.

Grenadiers of the World Oceans: Biology, Stock Assessment, and Fisheries

<em>Abstract</em>.—A total of seven grenadier species were found in the waters of the Falkland Islands, two of them, <em>Macrourus carinatus </em>and <em>Macrourus holotrachys</em>, being of commercial importance. <em>M. carinatus </em>was found in catches of trawlers and longliners between 173 and 1,201 m. The maximum abundance of this species occurred between 700 and 1,000 m. <em>M. holotrachys </em>occurred between 291 and 1,770 m, mostly deeper than 900 m. <em>Coelorinchus fasciatus </em>was the most abundant among the small-sized species. It occurred between 114 and 982 m, mostly between 200 and 600 m. The maximum age was 37 years for <em>M. carinatus</em>, 26 years for <em>M. holotrachys </em>and 19 years for <em>C. fasciatus</em>. <em>Macrourus </em>spp. reproduce all year round, <em>C. fasciatus</em>—mostly in spring. The survey area (about ¼ of the entire Falkland slope between 500 and 1,000 m isobaths) harbored a biomass of <em>M. carinatus </em>of about 40,000 tons.

Grenadiers of the World Oceans: Biology, Stock Assessment, and Fisheries

<em>Abstract.—</em>The Mid-Atlantic Ridge of the North Atlantic is inhabited by at least 16 macrourid species in 9 genera. The species composition and distribution patterns are analysed based on bottom trawl catches in the depth range 985 to 3461m conducted on the 2004 MAR-ECO expedition between the Azores and the southern Reykjanes Ridge. Some of the species, e.g. roundnose grenadier <em>Coryphaenoides rupestris</em>, <em>C. brevibarbis </em>and abyssal grenadier <em>C. armatus, </em>rank among the most abundant demersal fishes on the ridge or in the deep axial valleys or fracture zones, while others are uncommon or rare. While a few species have apparently restricted northerly or southerly distributions, most are widespread. Among common species that occur along the entire ridge section investigated, there are indications of structuring by depth of occurrence.

Grenadiers of the World Oceans: Biology, Stock Assessment, and Fisheries

<em>Abstract.</em>—Available information on the grenadiers from the Colombian Caribbean is compiled. Depth and latitudinal distribution of reported species are shown and briefly discussed. In view of the scarcity of data and the planned extension of the fishery frontier to deep waters, emphasis is made on the need of research for future protection of populations and regulation of the fishery.

Grenadiers of the World Oceans: Biology, Stock Assessment, and Fisheries

<em>Abstract.</em>—This report summarizes biological, fishery, and survey information on giant grenadier, <em>Albatrossia pectoralis</em>, in Alaskan waters. Catch estimates of giant grenadier in Alaska for the years 1997–2005 have averaged over 16,000 metric tons (mt), and most of this catch has been taken as bycatch in longline fisheries for sablefish, <em>Anoplopoma fimbria</em>, and Greenland halibut, <em>Reinhardtius hippoglossoides</em>. The giant grenadier catch is all discarded, and none of the fish survive due to the pressure change when they are brought to the surface. Most of the catch is from the Gulf of Alaska. Data from bottom trawl and longline surveys in Alaska indicate that giant grenadier are extremely abundant in depths 300–1,000 m, and it appears this species is very important ecologically in this environment. Greatest abundance is in the western Gulf of Alaska, eastern Aleutian Islands, and in some areas of the eastern Bering Sea; abundance declines in the eastern Gulf of Alaska. Relative abundance of giant grenadier is much higher off Alaska than off the U.S. West Coast. Fish in the eastern Bering Sea and Aleutian Islands were consistently larger than those in the Gulf of Alaska. Mean size of females was larger in shallower water, and decreased with depth. Females and males appear to have different depth distributions, with females greatly predominating in depths less than 800 m. Although sex composition of giant grenadier caught in the fishery is unknown, nearly all the fishing effort is believed to be in waters less than 800 m, which indicates females are disproportionately harvested. Because of the great abundance of giant grenadier in Alaska and the relatively modest catch, overfishing of giant grenadier does not appear to be a problem at present. However, because information on the population dynamics of giant grenadier is very sparse, and because of the 100% discard mortality, the disproportionate harvest of females, and the general susceptibility of deep-sea fish to overharvest, fishery managers should monitor this species closely if catches increase in the future.