Patterns of color phase indicate spawn timing at a Nassau grouper Epinephelus striatus spawning aggregation

Nassau grouper Epinephelus striatus are a large bodied, top level predator that is ecologically important throughout the Caribbean. Although typically solitary, Nassau grouper form large annual spawning aggregations at predictable times in spe- cific locations. In 2003, The Cayman Islands Marine Conservation Board established protection for a newly rediscovered Nassau grouper spawning aggregation on Little Cayman, British West Indies. The large size of this aggregation provides a unique oppor- tunity to study the behavior of Nassau grouper on a relatively intact spawning aggregation. During non-spawning periods Nassau grouper display a reddish-brown-and-white barred coloration. However, while aggregating they exhibit three additional color phases： ＂bicolor＂, ＂dark＂, and ＂white belly＂. We video sampled the population on multiple days leading up to spawning across five spawning years. Divers focused a laser caliper equipped video camera on individual fish at the aggregation. We later ana- lyzed the video to determine the length of the fish and record the color phase. Our observations show that the relative proportion of fish in the bicolor color phase increases significantly on the day leading up to the primary night of spawning. The increase in the proportion of the bicolor color phase from 0.05 early in the aggregation to 0.40 on the day of spawning suggests that this color phase conveys that a fish is behaviorally and physiologically prepared to spawn. Additionally, 82.7% of fish exhibiting dark or white belly coloration early in the aggregation period suggests that these color phases are not only shown by female fish as was previously posited [Current Zoology 58 （1）： 73-83, 2012].

Spatial and temporal distributions and some biological aspects of commercially important fish species of Lake Tana,Ethiopia

Objective:To know spatial,temporal distributions and some biological aspects of commercially important fish species of Lake Tana.Methods:Distribution of fish species in Lake Tana was studied from November 2009 to October 2012 based on samples collected every other month using gillnets of 60,80,100,120 and 140 mm stretched mesh sizes.Labeobarbus species,Clarias gariepinus,Oreochromis niloticus,and Varicorhinus beso are commercially important fish species and form 68%,18%,14%and 0.5%of the pooled experimental fish catch.There was significant variability among years and sampling sites of both temporal and spatial aspects;Mann-Whitney U tests were used for pair wise comparisons of sites and years.Results:The composition of Labeobarbus spp.and Varicorhinus beso shows significant decline.On the other hand,the composition of Oreochromis niloticus did not change,but Clarias gariepinus increased by 100%by catch composition.The most likely explanations for the total decline in abundance of fish species are the increase of the illegal commercial gillnet fishery targeting their spawning aggregations in the wetlands and river mouths,and the increasing trend of the degradation of spawning and nursery habitats both in the lake and major tributary rivers of the catchment area.Conclusions:There should be a need for urgent development of a management plan focusing on ensuring sustainable utilization of a resource by fishing effort,gear mesh size and gear type restrictions,and controlling the spawning grounds from different types of human encroachment and designing closing seasons and spawning grounds during the breeding seasons of different fish species of Lake Tana.

Assessing potential protection effects on commercial fish species in a Cuban MPA

Cuba has been leading marine protected area(MPA)designation in the Caribbean region to ensure conservation of its valuable marine ecosystems.Yet,an efficient monitoring program for MPAs is still to be implemented and will benefit from pre-existing information.The highly regulated MPA of Punta Francés National Park is one of the first Cuban MPAs and was established mainly to protect species and ecosystems for tourism purposes.Monitoring of protection effects on commercial fish species was lacking in this MPA.This study aimed at increasing local scientific knowledge by providing a baseline study about the most commercially fished families(Haemulidae,Lutjanidae and Serranidae)around Punta Francés MPA.Data collected represent only a limited period but can be used as a base point to support future monitoring.Fish abundance in number and biomass,and size were collected to test for differences between inside and adjacent areas outside the Punta Francés MPA,in different coral reef types.The main result of this study was the significantly larger size and biomass of snappers and groupers outside the MPA where intense fisheries occur.An observation consistent with a large spawning aggregation was also recorded outside the MPA.Even with a limited set of data,these results suggest that,at least temporarily,the most targeted species[and sizes]are still highly vulnerable to fisheries.Relevant habitats in the adjacent area,that are apparently missing within the MPA,may support some of the results found.Extending the limits of the Punta Francés MPA to include those habitats outside may be critical to ensure the effectiveness of this MPA in contributing to protect the most commercial species of the region.This should be done together with efficient fisheries management measures in the region,such as the significantly increase of minimum legal sizes and temporal closures during spawning migrations.