Toward identification of larval sailfish (Istiophorus platypterus), white marlin (Tetrapturus albidus), and blue marlin (Makaira nigricans) in the western North Atlantic Ocean*

The identification of larval istiophorid billfishes from the western North Atlantic Ocean has long been problematic. In the present study, a molecular technique was used to positively identify 27 larval white marlin (Tetrapturus albidus), 96 larval blue marlin (Makaira nigricans), and 591 larval sailfish (Istiophorus platypterus) from the Straits of Florida and the Bahamas. Nine morphometric measurements were taken for a subset of larvae (species known), and lower jaw pigment patterns were recorded on a grid. Canonical variates analysis (CVA) was used to reveal the extent to which the combination of morphometric, pigment pattern, and month of capture information was diagnostic to species level. Linear regression revealed species-specific relationships between the ratio of snout length to eye orbit diameter and standard length (SL). Confidence limits about these relationships served as defining characters for sailfish >10 mm SL and for blue and white marlin >17 mm SL. Pigment pattern analysis indicated that 40% of the preflexion blue marlin examined possessed a characteristic lower jaw pigment pattern and that 62% of sailfish larvae were identifiable by lower jaw pigments alone. An identification key was constructed based on pigment patterns, month of capture, and relationships between SL and the ratio of snout length to eye orbit diameter. The key yielded identifications for 69.4% of 304 (blind sample) larvae used to test it; only one of these identifications was incorrect. Of the 93 larvae that could not be identified by the key, 71 (76.3%) were correctly identified with CVA. Although identif ication of certain larval specimens may always require molecular techniques, it is encouraging that the majority (92.4%) of istiophorid larvae examined were ultimately identifiable from external characteristics alone.

An approach to estimate the natural mortality rate in fish stocks

A simple approach is introduced to estimate the natural mortality rate (M) of fish stocks. The approach is based on the age at maximum cohort biomass, or critical length (L*) concept. The ratio of the critical length to the asymptotic length ( = L*/L8) is relatively constant in 141 fish stocks at 0.62 (CV = 21.4 per cent) and the relationship M = 3K(1- )/ is derived and could be used to estimate M, where K is the growth coefficient of the von Bertalanffy growth function. Average values of are given for the various Families of fish in order to estimate M based on closely related species.

Clam farming in the Mekong Delta, Vietnam

The Mekong Delta region in southern Vietnam has high potential for coastal aquaculture, including mollusc culture. Many mollusc species are cultured for domestic and export markets including white clam (Meretrix lyrata Showerby) and blood cockle (Arca granosa). Techniques for clam farming include the nursery and grow-out phases. At present, there are approximately 600 coastal families engaged in clam farming over a total area of 1,870 ha, of which 82.63% is used for the grow-out phased and 17.7% for the nursery phase. Nursery areas are near the coast and receive less than 5 hours of sunlight per day. The average area for a nursery is 3-4 ha and it is fenced with a net or bamboo stakes to prevent clams from escaping and to prevent water currents from carrying them away. Grow-out farm areas are further from the coast and are exposed to sunlight for only 2-3 hours/day. Average farm area for grow-out is 5-6 ha, and may or may not be fenced. Average operating cost is US$1100 per ha for nursery and US$757 per ha for grow-out (the cost of capital assets are not included) with loans being the main source of financial. Problems for clam farmers in the area include natural phenomena, inadequate culture techniques, lack of financing or credit systems, and marketing. Environment-related problems that cause clam mortality include flooding, and freshwater effluent and siltation or sedimentation from Mekong River. Other problems that constrain the development of clam culture in the area are: marketing problems such as lack of buyers and price fluctuations; exploitation of the natural clam populations.

Distribution of Belugas, Delphinapterus leucas, in Cook Inlet, Alaska, During June/July 1993–2000

Aerial surveys of belugas, Delphinapterus leucas, in Cook Inlet wre flown each year during June and/or July from 1993 to 2000. This project was designed to delineate distribution and collect aerial counts, elements critical to the managment of this small, isolated stock that was subjected to a persistent harvest by Native hunters. The surveys provided a thorough, annual coverage of the coastal areas of the inlet (1,300 km of shoreline) and included roughly 1,000 km of offshore transects annually. Coastal transects were flown 1.4 km from the waterline, thus surveying most of the area within 3 km of shore. These, along with offshore transects, provided annual systematic searches of 13-33% of the entire inlet. The largest concentration of belugas (151-288 whales by aerial count) was in the northern portion of upper Cook Inlet in the Susitna River Delta and/or in Knik Arm. Another concentration (17-49 whales) was consistently found between Chickaloon River and Point Possession. Smaller groups (generally <20 whales) were occasionally found in Turn-again Arm, Kachemak Bay, Redoubt Bay (Big River), and Trading Bay (McArthur River) prior to 1995 but not thereafter. Over the past three decades, summer distribution has shrunk such that sightings now only rarely occur in lower Cook Inlet and in offshore areas. In the 1990's, most (96-100%) of the sightings were concentrated in a few dense groups in shallow areas near river mouths in upper Cook Inlet.

Beluga, Delphinapterus leucas, Group Sizes in Cook Inlet, Alaska, Based on Observer Counts and Aerial Video

Belugas, Delphinapterus leucas, groups were videotaped concurrent to observer counts during annual NMFS aerial surveys of Cook Inlet, Alaska, from 1994 to 2000. The videotapes provided permanent records of whale groups that could be examined and compared to group size estimates ade by aerial observers.Examination of the video recordings resulted in 275 counts of 79 whale groups. The McLaren formula was used to account for whales missed while they were underwater (average correction factor 2.03; SD=0.64). A correction for whales missed due to video resolution was developed by using a second, paired video camera that magnified images relative to the standard video. This analysis showed that some whales were missed either because their image size fell below the resolution of hte standard video recording or because two whales surfaced so close to each other that their images appeared to be one large whale. The correction method that resulted depended on knowing the average whale image size in the videotapes. Image sizes were measured for 2,775 whales from 275 different passes over whale groups. Corrected group sizes were calcualted as the product of the original count from video, the correction factor for whales missed underwater, and the correction factor for whales missed due to video resolution (averaged 1.17; SD=0.06). A regression formula was developed to estimate group sizes from aerial observer counts; independent variables were the aerial counts and an interaction term relative to encounter rate (whales per second during the counting of a group), which were regressed against the respective group sizes as calculated from the videotapes. Significant effects of encounter rate, either positive or negative, were found for several observers. This formula was used to estimate group size when video was not available. The estimated group sizes were used in the annual abundance estimates.

SAMUDRA Report No. 62, July 2012

Contents: Customary Rights in South Africa. Artisanal Fishworkers of Brazil. US Waterfronts. Sea Piracy in Nigeria. Civil Society Guidelines on SSF. SBSTTA 16th Session.

Stanford oceanographic expedition 17, Galapagos Islands and vicinity, 22 February-23 March 1968: observations on birds, the Galapagos fur seal, and cetaceans

1. Systematic list of birds (pp. 23-31) 2. Observations on the Galapagos fur seal, Arctocephalus australis galapagoensis Heller, 1904 (pp. 31-33) 3. Cetaceans observed (pp. 33-34)

Southern California's megaflood event of ca. 1605 AD linked to large-scale atmospheric forcing

A distinct, 1- to 2-cm-thick flood deposit found in Santa Barbara Basin with a varve-date of 1605 AD ± 5 years testifies to an intensity of precipitation that remains unmatched for later periods when historical or instrumental records can be compared against the varve record. The 1605 AD ± 5 event correlates well with Enzel's (1992) finding of a Silver Lake playa perennial lake at the terminus of the Mojave River (carbon-14-dated 1560 AD ± 90 years), in relative proximity to the rainfall catchment area draining into Santa Barbara Basin. According to Enzel, such a persistent flooding of the Silver Lake playa occurred only once during the last 3,500 years and required a sequence of floods, each comparable in magnitude to the largest floods in the modern record. To gain confidence in dating of the 1605 AD ± 5 event, we compare Southern California's sedimentary evidence against historical reports and multi-proxy time-series that indicate unusual climatic events or are sensitive to changes in large-scale atmospheric circulation patterns. The emerging pattern supports previous suggestions that the first decade of the 17th century was marked by a rapid cooling of the Northern Hemisphere, with some indications for global coverage. A burst of volcanism and the occurrence of El Nino seem to have contributed to the severity of the events. The synopsis of the 1605 AD ± 5 years flood deposit in Santa Barbara Basin, the substantial freshwater body at Silver Lake playa, and much additional paleoclimatic, global evidence testifies for an equatorward shift of global wind patterns as the world experienced an interval of rapid, intense, and widespread cooling.

St. John, USVI mission report, NOAA/NOS/NCCOS/CCMA/Biogeography Branch, July 6 - July 17, 2009

The intent of this field mission was to continue ongoing efforts: (1) to spatially characterize and monitor the distribution, abundance and size of reef fishes, and the abundance of macroinvertebrates (conch, Diatema, lobster) within and around the waters of the Virgin Islands National Park (VIIS) and newly established Virgin Islands Coral Reef National Monument (VICR), (2) to correlate this information to in-situ data collected on associated habitat parameters, (3) to use this information to establish the knowledge base necessary for enacting management decisions in a spatial setting and (4) to establish the efficacy of those management decisions. An additional focus this year, was to evaluate a new habitat data collection method for RHA sites (MSR and some Coral Bay sites). There are concerns that the cylinder habitat data are not reflective of the fish transect habitat. To address this, we collected habitat data at 5x4 m increments along the transect in addition to data collected using the cylinder method. We are currently assessing the potential differences between these methods and preliminary results indicate that the average difference of coral cover estimates between the two methods was 4.1% (range 0-11%) based on 16 sample sites. In addition, Erinn Muller, a Nancy Foster Fellowship recipient, collaborated with the Biogeography Branch to examine the spatial distribution of coral diseases, to provide baseline information on disease prevalence over varying spatial scales and to establish spatial distributions of coral diseases around St. John.