Toward sustainable management of small cetacean fisheries around Japan

Abstract:   The management of Japanese domestic fisheries for small cetaceans has been based on a traditional approach that involves only the best set of assumptions and data. However, uncertainty, which is pervasive and inevitable for most fisheries resources, often leads the traditional approach to serious failure. Here is presented the basic framework of a simulation-based approach with a simple Bayesian method that is applicable to Japanese fisheries for small cetaceans. For illustration, the simulation model was applied to Dall's porpoise data in order to investigate the robustness of several management procedures against uncertainty. The simulation showed that the current management procedure, based on only the best values, could fail to manage the stocks at a considerably high probability. However, the use of the conservative management procedure, potential biological removal, permits the sustainable harvesting of Dall's porpoise for at least 100 years into the future, even under uncertainty. In conjunction with a firm structure for implementation of management procedures, the spread of simulation-based approaches will quickly enable successful sustainable management of small cetaceans.     

Reversal of interlaminar signal between sensory and memory processing in monkey temporal cortex

The primate temporal cortex implements visual long-term memory. However, how its interlaminar circuitry executes cognitive computations is poorly understood. Using linear-array multicontact electrodes, we simultaneously recorded unit activities across cortical layers in the perirhinal cortex of macaques performing a pair-association memory task. Cortical layers were estimated on the basis of current source density profiles with histological verifications, and the interlaminar signal flow was determined with cross-correlation analysis between spike trains. During the cue period, canonical "feed-forward" signals flowed from granular to supragranular layers and from supragranular to infragranular layers. During the delay period, however, the signal flow reversed to the "feed-back" direction: from infragranular to supragranular layers. This reversal of signal flow highlights how the temporal cortex differentially recruits its laminar circuits for sensory and mnemonic processing.     

Total synthesis of norzoanthamine

Norzoanthamine, an alkaloid isolated from Zoanthus sp., can suppress the loss of bone weight and strength in ovariectomized mice. Norzoanthamine derivatives can also strongly inhibit the growth of P-388 murine leukemia cell lines and human platelet aggregation. However, norzoanthamine's densely functionalized complex stereostructure and scarce availability from natural sources have proved a synthetic challenge. We report the stereoselective total synthesis of norzoanthamine in 41 steps, with an overall yield of 3.5% (an average of 92% yield each step).     

Community-level impacts induced by introduced largemouth bass and bluegill in farm ponds in Japan

Largemouth bass Micropterus salmoides and bluegill Lepomis macrochirus have been introduced into many countries and have become cosmopolitan exotic species. However, only a few studies show their impact on introduced communities. To investigate their impact, we performed natural snapshot experiments in 15 farm ponds in Saitama prefecture, eastern Japan. We selected 10 and 5 small ponds in similar environmental conditions, but with and without exotics, respectively. The numbers of fish, crustaceans, and nymphal odonates were smaller in ponds where exotics were found and some species were considered to be locally extinct in several ponds. On the other hand, the numbers of benthic organisms, i.e. tadpoles, chironomids, chaoborids, and Oligochaeta were more abundant in ponds with exotics. These two groups of organisms were separated clearly on the first axis of DCA, which indicats that this difference was mainly induced by bass predation. This result suggests a trophic cascade in which top-down effects induced by exotics propagated to fish, crustaceans, and nymphal odonates directly and to some benthic organisms indirectly. Therefore, when one is to conserve native organisms, attention should be paid not only to direct negative effects, but also to indirect effects propagating to various trophic levels. Because farm ponds are typical Japanese small lentic systems having rich biodiversities and bass and bluegill have been shown to change farm pond communities widely, conservational treatments including eradication of exotic fish should be conducted immediately.     

New Synthetic Lures for the Male Melon Fly

Several para-substituted derivatives of 4-phenyl-2-butanone (I) have proved to be powerful attractants for the male melon fly (Dacus clucurbitae). These compounds, unlike anisylacetone, heretofore the best lure, attract even newly emerged flies. The most potent analog is 4-(p-acetoxyphenyl)-2-butanone (II), which also strongly attracts Dacus ochrosiae males.     

Evidence of global chlorophyll d

Although analyses of chlorophyll d (Chl d)-dominated oxygenic photosystems have been conducted since their discovery 12 years ago, Chl d distribution in the environment and quantitative importance for aquatic photosynthesis remain to be investigated. We analyzed the pigment compositions of surface sediments and detected Chl d and its derivatives from diverse aquatic environments. Our data show that the viable habitat for Chl d-producing phototrophs extends across salinities of 0 to 50 practical salinity units and temperatures of 1 degrees to 40 degrees C, suggesting that Chl d production can be ubiquitously observed in aquatic environments that receive near-infrared light. The relative abundances of Chl d derivatives over that of Chl a derivatives in the studied samples are up to 4%, further suggesting that Chl d-based photosynthesis plays a quantitatively important role in the aquatic photosynthesis.