Managing global shark fisheries: Suggestions for prioritizing management strategies

1. Over the past two decades the number of fisheries targeting shark resources has increased dramatically. A combination of factors, including relatively slow growth rate, low fecundity and late age of maturity, result in low recovery rates from exploitation for most shark species. This, in turn, is reflected in the poor record of sustainability of shark fisheries. 2. One of the greatest challenges is to find a way to deal with the substantial levels of shark bycatch taken in many non-target fisheries. Poor general recording of shark landings and paucity of shark landing data at the species level also undermine the development of effective shark management strategies. 3. This paper reviews the problems that must be faced worldwide if shark resources are to be managed sustainably and lays out a comprehensive set of prioritized management strategies to facilitate the sustainable management of global shark fisheries. It is acknowledged that the majority of sharks are harvested in developing countries and that the management of shark resources in developing and developed countries will need to incorporate different management strategies relevant to local socio-economic agendas. The management recommendations deal with methods to improve the global regulation of fisheries, ways to improve global conservation ethics and encourage active participation in management, as well as means by which specific management strategies may be implemented. Copyrigh

Cognitive abilities in Malawi cichlids (Pseudotropheus sp.): matching-to-sample and image/mirror-image discriminations.

The ability to recognize and distinguish between visual stimuli is fundamental for everyday survival of many species. While diverse aspects of cognition, including complex visual discrimination tasks were previously successfully assessed in fish, it remains unknown if fish can learn a matching-to-sample concept using geometrical shapes and discriminate between images and their mirror-image counterparts. For this purpose a total of nine Malawi cichlids (Pseudotropheus sp.) were trained in two matching-to-sample (MTS) and three two-choice discrimination tasks using geometrical, two-dimensional visual stimuli. Two out of the three discrimination experiments focused on the ability to discriminate between images and their mirror-images, the last was a general discrimination test. All fish showed quick associative learning but were unable to perform successfully in a simultaneous MTS procedure within a period of 40 sessions. Three out of eight fish learned to distinguish between an image and its mirror-image when reflected vertically; however none of the fish mastered the task when the stimulus was reflected horizontally. These results suggest a better discrimination ability of vertical compared to horizontal mirror-images, an observation that is widespread in literature on mirror-image discrimination in animals. All fish performed well in the general visual discrimination task, thereby supporting previous results obtained for this species

Notes on female reproductive biology and embryos of the brown guitarfish Rhinobatos schlegelii from the Penghu Islands, Taiwan

Litter size and details of the reproductive biology of female brown guitarfish Rhinobatos schlegelii from the Penghu Islands, Taiwan, are provided for the first time. Litter size ranged 1–14 (mean 8.5), with an embryonic sex ratio of 1:1. Vitellogenesis proceeded in parallel with gestation

Stimulus sequences used in experiment 1a.

<p>The composition of four different predetermined sequences A-D (PowerPoint presentations), containing 10 trials each, used in experiment 1a. For each trial, the positive stimulus that served as sample and corresponding stimulus and its position are shown. The negative stimulus that served as distracting stimulus is also shown for each trial. P =  positive stimulus; N =  negative stimulus; + =  cross; o =  circle; R =  right; L =  left.</p

Visual two-dimensional stimuli used in this study.

<p>(A) open circle, (B) cross, (C) filled triangle, (D) reversed letter ‘T’, (E) F-shaped form, (F) U-shaped form, (G) line drawing of a fish, (H) asymmetrical shape, (I) star, (J) letter ‘R’, (K) filled square.</p

Overview of the different MTS and two-choice discrimination experiments.

<p>Short information is given concerning the performed experiments and therein used methods and stimuli.</p

Training achievements for all individuals used in part B and C of experiment 2a.

<p>The colored lines display the individual learning success for each fish that reached criterion, shown by the percentage of correct choices per session (à 10 trials). The dashed red line indicates the threshold for the learning criterion at 70 % correct choices. The three sessions necessary to reach criterion (≥70 % correct choices) are highlighted by big dots colored analogous to the individual learning curves.</p

Example of a sequence of PowerPoint slides used in a trial of experiment 1a.

<p>The figure shows the chronology of a possible sequence used in a trial of experiment 1a, consisting of three slides presenting the stimuli in a simultaneous MTS. The timeline indicates the duration of each slide's presentation in seconds. The last slide denotes the ITI.</p