Increased predation of juvenile European spiny lobster (Palinurus elephas) in a marine protected area

One of the aims of Mediterranean marine protected areas (MPAs) is to increase populations of exploited species, such as the European spiny lobster (Palinurus elephas), which is considered a key species for its commercial and ecological value. Monitoring of temporal patterns in abundance of early benthic stages of P. elephas indicated that predation may be higher inside the Medes Islands MPA relative to adjacent control sites. Tethering experiments were performed to test whether predation rates actually differed within and outside the MPA. Relative mortality of recently‐settled juveniles inside the MPA was much higher than in control sites in adjacent non‐protected areas. Treatments with and without shelter indicated that predation on recently‐settled juvenile spiny lobsters was moderated by the availability of suitable shelter. The decline or absence of fish predators in the fished area may be the reason why juvenile lobsters outside the MPA experience lower predation than within the MPA.     

Impact of minimum legal size increases on egg‐per‐recruit production,size structure,and ovigerous females in the American lobster (Homarus americanus) population off the Magdalen Islands (Quebec,Canada): A case study

In the mid 1990s, American lobster (Homarus americanus) from Canadian waters was considered overfished based on estimated levels of egg‐per‐recruit production (EPR). In 1997, the Department of Fisheries Oceans responded by adopting a goal of doubling the level of EPR from its 1996 level. In the Magdalen Islands (Quebec), results from a simulation model indicated that doubling EPR could be reached by increasing the minimum legal size (MLS) from 76 mm to 83 mm carapace length. This was done at a pace of 1 mm per year from 1997 to 2003. Following the increase of MLS, the size structure, mean size, and the abundance of ovigerous females improved significantly in the catches. However, levels of fishing effort are still very high. This could cause undesirable effects such as altering sex ratios and size structure of males, which could lead to sperm limitation, and reducing the contribution of multiple spawners to egg production, which could become an issue if egg quality is important. Consideration of these issues leads to the recommendation of a multidimensional approach to lobster conservation.     

Modelling the effects of Marine Protected Areas (MPAs) on the southern rock lobster (Jasus edwardsii) fishery of Victoria,Australia

Since 2002, 5.3% of the Victorian coastal waters have been declared as Marine Protected Areas (MPAs). These are aimed at safeguarding important marine habitats and species, significant natural features, and areas of cultural heritage and aesthetic value. However, MPAs impact the fishery for southern rock lobster (Jasus edwardsii), as total allowable catches (TACs) were previously set to allow the biomass to recover to pre‐specified target levels. The model on which assessments and risk analyses are based is extended to include the impact of MPAs. The MPAs and the area open to fishing are modelled as subpopulations with different levels of mortality and consequently different density and population size‐structure. A range for the probability of a lobster moving from a MPA to the fished area from 0 to 15% is considered, based on the results of tagging studies. The reduction of biomass available to the commercial fishery because of the introduction of MPAs is estimated to be 8% and 16% (Western and Eastern Zones) respectively. The results of a risk assessment show that if the current TACs are maintained, the time to increase the biomass available to the commercial fishery by 50% would be delayed 5–9 years in the Western Zone and 1–4 years in the Eastern Zone because of the impact of displaced effort. In contrast, spawning biomass in the Eastern Zone is currently below the agreed limit reference point, and the introduction of MPAs would enhance the rate of recovery, although only marginally initially, faster than the absence of the MPAs.     

Evolution of operational management procedures for the South African West Coast rock lobster (Jasus lalandii) fishery

The commercial fishery for Jasus lalandii, the South Africa West Coast rock lobster, began in the late 1800s and at its peak in the early 1950s yielded an annual catch of 18 000 t. Although this annual catch has dropped to only some 2000 t over recent years, the fishery remains South Africa's third most valuable for landed value. The primary reason for the low total allowable catch (TAC) over these recent years has been a marked drop in somatic growth rate that occurred at the end of the 1980s, for reasons that remain unexplained. A key problem in formulating TAC recommendations with longer‐term objectives in mind, has been uncertainties about likely future trends, particularly in somatic growth and recruitment. To address this problem, an “operational management procedure” (OMP) was adopted in 1997 and has twice been re‐evaluated and modified (in 2000 and 2003) in the light of further data and changing perceptions of resource dynamics. The history of this process is reviewed, concentrating on the most recent modification. In particular, a summary is given of the process by which the merits of alternative management procedures were evaluated over a range of important uncertainties about the dynamics of the resource. This summary includes a discussion of the key trade‐offs between resource rebuilding, future TAC trends and TAC variability, and the eventual choice that was made. The paper concludes by listing a number of lessons learnt concerning best practice for OMP development as this process evolved.     

Estimating the sustainable lobster (Panulirus ornatus) catch in Torres Strait,Australia, using an age-structured stock assessment model

The ornate rock lobster (Panulirus ornatus) is distributed across Torres Strait between Australia and Papua New Guinea and supports the most important commercial fishery to Islanders in the region. The long-term sustainability of the fishery is of importance not only to local island communities but also to the bilateral relationship between the two countries. In this paper, we developed an age-structured fishery model to assess the current stock status and estimate the long-term sustainable catch. The model was fitted to catch statistics and survey-based population estimates through a weighted maximum likelihood approach. Natural mortality was estimated at 0.732 yr⁻¹, and fishing mortality ranged from 0.19 to 0.65 yr⁻¹ from 1989 to 2005. The maximum sustainable yield was estimated at about 640 tonnes whole weight with a corresponding fishing mortality of 0.5 yr⁻¹. A stock–recruitment model was established based on outputs of the stock assessment model. To obtain the maximum sustainable yield, spawning stock should be maintained at 120×10⁴ lobsters. The lobster spawning stock has been fished down below this level twice since 1989, in 1999 and 2002, and was higher than this level in 2004 and 2005. These results suggest that the Torres Strait lobster stock is not over-fished and that the current harvest strategy is likely to maintain the stock at or above the level that would support the maximum sustainable yield if the current cap on fishing effort remains in place.     

2016年夏秋季南极布兰斯菲尔德海峡威氏棘冰鱼脂肪酸组成及其食性指示研究

作为20世纪70年代末期底拖网渔业的主要捕捞对象以及近年来南极磷虾渔业的兼捕对象之一,威氏棘冰鱼(Chaenodraco wilsoni)在海洋捕食者与饵料生物之间的能量流动中起着重要的传递作用,而目前针对该鱼种的营养特性及其食性的研究却十分有限。为此,本研究分析了布兰斯菲尔德海峡威氏棘冰鱼肌肉组织中脂肪酸的含量及其组成,并进一步探讨特征脂肪酸对食性的指示。结果表明,体长范围为4.8—30.7 cm、质量范围为0.3—250.5 g的威氏棘冰鱼肌肉样本中共检测出29种脂肪酸,其中含量较高的脂肪酸包括C16:0,C18:0,C18:1n9c,C20:5n3(EPA)以及C22:6n3(DHA),各类脂肪酸类型含量由高至低依次为多不饱和脂肪酸(PUFA),饱和脂肪酸(SFA)以及单不饱和脂肪酸(MUFA)。威氏棘冰鱼多种特征脂肪酸含量与体长之间不具显著的相关关系,表明其摄食并不随着个体的生长而发生较大的变化。秋冬季威氏棘冰鱼呈现杂食性特性,主要摄食以硅藻为食的生物,如南极磷虾(Euphausia superba); 同时对底栖生物和海底碎屑也有一定的摄食,并会摄食一定量的桡足类生物。)     

Physico‐chemical features of pupu springs

The physical and chemical features of Pupu Springs (40 51’ S, 172° 46’ E), near Takaka, the largest cold springs in New Zealand and one of the largest in the world, were investigated by scuba diving. The springs have a maximum depth of 6.9 m and a mosaic of substrate types (bedrock, boulders, and gravel). The temperature of the springs water is constant at 11.7°C, water velocities are generally moderate to very strong (25–100 cm.s^‐1), and average water discharge is about 9.6 m³.s^‐1. Mean holding time for water in the springs is 4.4 min. The water is extremely clear, with a vertical extinction coefficient (log10) of 0.09. The springs water flows from an artesian basin in Arthur Marble and is low in dissolved oxygen. The water is rich in calcium (64 g.m^‐3), with a high specific conductivity (65 mS.m^‐1). Information on water temperature, discharge, and chemistry is provided for five other cold springs in New Zealand: Hamurana Springs, Rotorua; Otangaroa Springs, near Putaruru; Three Springs, near Fairlie; Western Springs, Auckland; and a spring at Lake Hayes, Queenstown.     

Management strategy evaluation for rock lobster,Jasus edwardsii,off Victoria,Australia: Accounting for uncertainty in stock structure

The management strategy evaluation (MSE) approach was used to evaluate management strategies based on the current method of stock assessment for rock lobster (Jasus edwardsii) off Victoria, Australia, and decision rules inferred from the management plan for Victorian rock lobster and past practice when selecting total allowable catches, TACs. The results are expressed in terms of whether it is possible to keep stocks above limit reference points with high probability and recover over‐exploited stocks to the target level. Three categories of management strategy were examined using the MSE, which differed in whether assessments were conducted, and TACs set, by management zone or by region within management zone. A management strategy based on conducting assessments and setting TACs by management zone is most similar to the way assessments are currently conducted and management regulations implemented for rock lobster off Victoria. However, this management strategy performed poorest in recovering stocks to target levels. Alternative management strategies which involved conducting assessments and setting TACs by region performed better, but may have practical limitations. The assessment method was found to be generally relatively accurate and precise, although estimation performance was poor/imprecise on occasion.     

Phase distribution of tidal constituents around New Zealand

The phase distributions of the M₂, S₂, K₁, and O₁ tidal constituents around New Zealand are plotted from existing harmonic analyses of tidal heights. Both semidiurnal constituents exhibit a complete 360° range of phase around New Zealand, with complex areas of rapid phase change through or near the strait separating the two main islands. The K₁ amphidrome and that for O₁, which previously were thought to be centred on New Zealand, are shown to be located cast of New Zealand. The distributions plotted highlight areas where tidal observations are lacking.